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Статті в журналах з теми "Strongly annular function":
1
Monahan, Adam H., and John C. Fyfe. "On Annular Modes and Zonal Jets." Journal of Climate 21, no. 9 (May 1, 2008): 1963–78. http://dx.doi.org/10.1175/2007jcli1841.1.
Анотація:
Abstract This study considers the relation of the annular mode to the kinematics of a fluctuating jet in zonal-mean zonal wind and to the zonal index, using an idealized model of fluctuations in the eddy-driven jet. When the sphericity of the domain is accounted for, observed and numerically simulated annular modes for the Southern Hemisphere summertime are found to be in excellent agreement. In particular, the annular mode and zonal index mode are shown to be related but distinct. Although the annular mode is strongly (but not identically) related to fluctuations in jet position, fluctuations in jet strength and width are shown to also be important for its simulation. When the sphericity of the domain is neglected, analytic expressions for the leading empirical orthogonal function (EOF) modes of zonal-mean geopotential for the cases of individual fluctuations in jet strength, position, and width can be obtained. None of these EOF modes have the characteristics of the annular mode. In the presence of simultaneous fluctuations in jet strength and position, the leading zonal-mean geopotential EOF mode (strongly resembling the annular mode) is shown to mix the zonal index mode of zonal-mean zonal wind with other EOF modes, demonstrating why the annular mode and zonal index mode are related but distinct. The greater sensitivity to domain size of EOF modes of geopotential relative to the EOF modes of zonal-mean zonal wind is also discussed. This study focuses on the Southern Hemisphere summertime, which is characterized by a single, eddy-driven jet; the generality of the results presented suggest that the conclusions should be qualitatively unchanged in the presence of both subtropical and eddy-driven jets.
2
Jalali, Mohammad Hadi, and Behrooz Shahriari. "Elastic Stress Analysis of Rotating Functionally Graded Annular Disk of Variable Thickness Using Finite Difference Method." Mathematical Problems in Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/1871674.
Анотація:
Elastic stress analysis of rotating variable thickness annular disk made of functionally graded material (FGM) is presented. Elasticity modulus, density, and thickness of the disk are assumed to vary radially according to a power-law function. Radial stress, circumferential stress, and radial deformation of the rotating FG annular disk of variable thickness with clamped-clamped (C-C), clamped-free (C-F), and free-free (F-F) boundary conditions are obtained using the numerical finite difference method, and the effects of the graded index, thickness variation, and rotating speed on the stresses and deformation are evaluated. It is shown that using FG material could decrease the value of radial stress and increase the radial displacement in a rotating thin disk. It is also demonstrated that increasing the rotating speed can strongly increase the stress in the FG annular disk.
3
MATHAI, STEPHEN C., CHRISTOPHER T. SIBLEY, PAUL R. FORFIA, JAMES O. MUDD, MICAH R. FISHER, RYAN J. TEDFORD, NOAH LECHTZIN, et al. "Tricuspid Annular Plane Systolic Excursion Is a Robust Outcome Measure in Systemic Sclerosis-associated Pulmonary Arterial Hypertension." Journal of Rheumatology 38, no. 11 (October 1, 2011): 2410–18. http://dx.doi.org/10.3899/jrheum.110512.
Анотація:
Objective.The tricuspid annular plane systolic excursion (TAPSE) strongly reflects right ventricular (RV) function and predicts survival in idiopathic pulmonary arterial hypertension (PAH). But its role in systemic sclerosis (SSc)-associated PAH has not been established. Our objective was to validate the TAPSE in the assessment of RV function and prediction of survival in SSc-PAH.Methods.Fifty consecutive patients with SSc-PAH who underwent echocardiography with TAPSE measurement within 1 h of clinically indicated right heart catheterization were followed prospectively. The relationship between TAPSE and measures of RV function and measures of survival was assessed.Results.The majority of the cohort were women in New York Heart Association class III/IV with severe PAH (mean cardiac index 2.4 ± 0.8 l/min/m2). RV function was significantly impaired (mean cardiac index 2.1 ± 0.7 vs 2.9 ± 0.8 l/min/m2; p < 0.01) and RV afterload was significantly greater (mean pulmonary vascular resistance 11.1 ± 5.1 vs 5.8 ± 2.5 Wood units; p < 0.01) in subjects with a TAPSE ≤ 1.7 cm. The proportion surviving in the low TAPSE group was significantly lower [0.56 (95% CI 0.37–0.71) and 0.46 (95% CI 0.28–0.62) vs 0.87 (95% CI 0.55–0.96) and 0.79 (95% CI 0.49–0.93), 1- and 2-year survival, respectively]. TAPSE ≤ 1.7 cm conferred a nearly 4-fold increased risk of death (HR 3.81, 95% CI 1.31–11.1, p < 0.01).Conclusion.TAPSE is a robust measure of RV function and strongly predicts survival in patients with PAH-SSc. Future studies are needed to identify the responsiveness of TAPSE to PAH-specific therapy and to assess its diagnostic utility in PAH-SSc.
4
Posson, H., and N. Peake. "The acoustic analogy in an annular duct with swirling mean flow." Journal of Fluid Mechanics 726 (June 10, 2013): 439–75. http://dx.doi.org/10.1017/jfm.2013.210.
Анотація:
AbstractThis paper is concerned with modelling the effects of swirling flow on turbomachinery noise. We develop an acoustic analogy to predict sound generation in a swirling and sheared base flow in an annular duct, including the presence of moving solid surfaces to account for blade rows. In so doing we have extended a number of classical earlier results, including Ffowcs Williams & Hawkings’ equation in a medium at rest with moving surfaces, and Lilley’s equation for a sheared but non-swirling jet. By rearranging the Navier–Stokes equations we find a single equation, in the form of a sixth-order differential operator acting on the fluctuating pressure field on the left-hand side and a series of volume and surface source terms on the right-hand side; the form of these source terms depends strongly on the presence of swirl and radial shear. The integral form of this equation is then derived, using the Green’s function tailored to the base flow in the (rigid) duct. As is often the case in duct acoustics, it is then convenient to move into temporal, axial and azimuthal Fourier space, where the Green’s function is computed numerically. This formulation can then be applied to a number of turbomachinery noise sources. For definiteness here we consider the noise produced downstream when a steady distortion flow is incident on the fan from upstream, and compare our results with those obtained using a simplistic but commonly used Doppler correction method. We show that in all but the simplest case the full inclusion of swirl within an acoustic analogy, as described in this paper, is required.
5
Carlhäll, C., L. Wigström, E. Heiberg, M. Karlsson, A. F. Bolger, and E. Nylander. "Contribution of mitral annular excursion and shape dynamics to total left ventricular volume change." American Journal of Physiology-Heart and Circulatory Physiology 287, no. 4 (October 2004): H1836—H1841. http://dx.doi.org/10.1152/ajpheart.00103.2004.
Анотація:
The mitral annulus (MA) has a complex shape and motion, and its excursion has been correlated to left ventricular (LV) function. During the cardiac cycle the annulus’ excursion encompasses a volume that is part of the total LV volume change during both filling and emptying. Our objective was to evaluate the contribution of MA excursion and shape variation to total LV volume change. Nine healthy subjects aged 56 ± 11 (means ± SD) years underwent transesophageal echocardiography (TEE). The MA was outlined in all time frames, and a four-dimensional (4-D) Fourier series was fitted to the MA coordinates (3-D+time) and divided into segments. The annular excursion volume (AEV) was calculated based on the temporally integrated product of the segments’ area and their incremental excursion. The 3-D LV volumes were calculated by tracing the endocardial border in six coaxial planes. The AEV (10 ± 2 ml) represented 19 ± 3% of the total LV stroke volume (52 ± 12 ml). The AEV correlated strongly with LV stroke volume ( r = 0.73; P < 0.05). Peak MA area occurred during middiastole, and 91 ± 7% of reduction in area from peak to minimum occurred before the onset of LV systole. The excursion of the MA accounts for an important portion of the total LV filling and emptying in humans. These data suggest an atriogenic influence on MA physiology and also a sphincter-like action of the MA that may facilitate ventricular filling and aid competent valve closure. This 4-D TEE method is the first to allow noninvasive measurement of AEV and may be used to investigate the impact of physiological and pathological conditions on this important aspect of LV performance.
6
Hassanzadeh, Pedram, and Zhiming Kuang. "The Linear Response Function of an Idealized Atmosphere. Part I: Construction Using Green’s Functions and Applications." Journal of the Atmospheric Sciences 73, no. 9 (August 10, 2016): 3423–39. http://dx.doi.org/10.1175/jas-d-15-0338.1.
Анотація:
Abstract A linear response function (LRF) determines the mean response of a nonlinear climate system to weak imposed forcings, and an eddy flux matrix (EFM) determines the eddy momentum and heat flux responses to mean-flow changes. Neither LRF nor EFM can be calculated from first principles owing to the lack of a complete theory for turbulent eddies. Here the LRF and EFM for an idealized dry atmosphere are computed by applying numerous localized weak forcings, one at a time, to a GCM with Held–Suarez physics and calculating the mean responses. The LRF and EFM for zonally averaged responses are then constructed using these forcings and responses through matrix inversion. Tests demonstrate that LRF and EFM are fairly accurate. Spectral analysis of the LRF shows that the most excitable dynamical mode, the neutral vector, strongly resembles the model’s annular mode. The framework described here can be employed to compute the LRF and EFM for zonally asymmetric responses and more complex GCMs. The potential applications of the LRF and EFM constructed here are (i) forcing a specified mean flow for hypothesis testing, (ii) isolating/quantifying the eddy feedbacks in complex eddy–mean flow interaction problems, and (iii) evaluating/improving more generally applicable methods currently used to construct LRFs or diagnose eddy feedbacks in comprehensive GCMs or observations. As an example for (iii), in Part II, the LRF is also computed using the fluctuation–dissipation theorem (FDT), and the previously calculated LRF is exploited to investigate why FDT performs poorly in some cases. It is shown that dimension reduction using leading EOFs, which is commonly used to construct LRFs from the FDT, can significantly degrade the accuracy owing to the nonnormality of the operator.
7
Massey, Richard John, Phoi Phoi Diep, Marta Maria Burman, Anette Borger Kvaslerud, Lorentz Brinch, Svend Aakhus, Lars Gullestad, Ellen Ruud, and Jan Otto Beitnes. "Impaired right ventricular function in long-term survivors of allogeneic haematopoietic stem-cell transplantation." Open Heart 8, no. 2 (December 2021): e001768. http://dx.doi.org/10.1136/openhrt-2021-001768.
Анотація:
AimsSurvivors of allogeneic haematopoietic stem-cell transplantation (allo-HSCT) are at higher risk of cardiovascular disease. We aimed to describe right ventricular (RV) systolic function and risk factors for RV dysfunction in long-term survivors of allo-HSCT performed in their youth.Methods and resultsThis cohort included 103 survivors (53% female), aged (mean±SD) 17.6±9.5 years at allo-HSCT, with a follow-up time of 17.2±5.5 years. Anthracyclines were used as first-line therapy for 44.7% of the survivors. The RV was evaluated with echocardiography, and found survivors to have reduced RV function in comparison to a group of healthy control subjects: Tricuspid annular plane systolic excursion, (TAPSE, 20.8±3.7 mm vs 24.6±3.8 mm, p<0.001), RV peak systolic velocity (RV-s’, 11.2±2.3 cm/s vs 12.3±2.3 cm/s, p=0.001), fractional area change (FAC, 41.0±5.2% vs 42.2±5.1%, p=0.047) and RV free-wall strain (RVFWS, −27.1±4.2% vs −28.5±3.3%, p=0.043). RV systolic dysfunction (RVSD) was diagnosed in 14 (13.6%), and was strongly associated with progressive left ventricular systolic dysfunction (LVSD). High dosages of anthracyclines were associated with greater reductions in RV and LV function. Multivariable linear regressions confirmed global longitudinal strain to be a significant independent predictor for reduced RV function.ConclusionImpaired RV function was found in long-term survivors of allo-HSCT who were treated in their youth. This was associated with progressive left ventricle dysfunction, and pretransplant therapies with anthracyclines. The occurrence of RVSD was less frequent and was milder than coexisting LVSD in this cohort.
8
de Beurs, K. M., and G. M. Henebry. "Northern Annular Mode Effects on the Land Surface Phenologies of Northern Eurasia." Journal of Climate 21, no. 17 (September 1, 2008): 4257–79. http://dx.doi.org/10.1175/2008jcli2074.1.
Анотація:
Abstract Land surface phenology (LSP) is the spatiotemporal development of the vegetated land surface as revealed by synoptic sensors. Modeling LSP across northern Eurasia reveals the magnitude, significance, and spatial pattern of the influence of the northern annular mode. Here the authors fit simple LSP models to two normalized difference vegetation index (NDVI) datasets and calculate the Spearman rank correlations to link the start of the observed growing season (SOS) and the timing of the peak NDVI with the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices. The relationships between the northern annular mode and weather station data, accumulated precipitation derived from the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) dataset, accumulated growing degree-days (AGDDs) derived from the NCEP–Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) reanalysis, and the number of snow days from the National Snow and Ice Data Center are investigated. The analyses confirm strong relationships between the temporal behavior of temperature and precipitation and large-scale climatic variability across Eurasia. The authors find widespread influence of the northern annular mode (NAM) on the land surface phenologies across northern Eurasia affecting 200–300 Mha. The tundra ecoregions were especially impacted with significant results for about a quarter of the biome. The influence of the AO was also extensive (>130 Mha) for the boreal forests. The AO appears to affect the Asian part of northern Eurasia more strongly than the NAO, especially for the NDVI peak position as a function of AGDD. Significant responses of vegetation timing to NAO and AO in northeastern Russia have not been as well documented as the seasonal advancement in Europe. The two Advanced Very High Resolution Radiometer NDVI datasets yield fields of LSP model parameter estimates that are more similar in dates of peak position than in dates for SOS and more similar for AO than for NAO. As a result, the authors conclude that peak position appears to be a more robust characteristic of land surface phenology than SOS to link vegetation dynamics to variability and change in regional and global climates.
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Pfaff, Marina, Michael F. G. Klein, Erich Müller, Philipp Müller, Alexander Colsmann, Uli Lemmer, and Dagmar Gerthsen. "Nanomorphology of P3HT:PCBM-Based Absorber Layers of Organic Solar Cells after Different Processing Conditions Analyzed by Low-Energy Scanning Transmission Electron Microscopy." Microscopy and Microanalysis 18, no. 6 (November 20, 2012): 1380–88. http://dx.doi.org/10.1017/s143192761201344x.
Анотація:
AbstractIn this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.
10
Gold, Jonathan, Yohei Akazawa, Mei Sun, Kendall S. Hunter, and Mark K. Friedberg. "Relation between right ventricular wall stress, fibrosis, and function in right ventricular pressure loading." American Journal of Physiology-Heart and Circulatory Physiology 318, no. 2 (February 1, 2020): H366—H377. http://dx.doi.org/10.1152/ajpheart.00343.2019.
Анотація:
Right ventricle (RV) pressure loading can lead to RV fibrosis and dysfunction. We previously found increased RV, septal hinge-point and left ventricle (LV) fibrosis in experimental RV pressure loading. However, the relation of RV wall stress to biventricular fibrosis and dysfunction is incompletely defined. Rabbits underwent progressive pulmonary artery banding (PAB) over 3 wk with hemodynamics, echocardiography, and myocardial samples obtained at a terminal experiment at 6 wk. An additional group received PAB and treatment with an endothelin receptor antagonist. The endocardial and epicardial borders of short-axis echo images were traced and analyzed with invasive pressures to yield regional end-diastolic (ED) and end-systolic (ES) wall stress. To increase clinical translation, computer model-derived wall stress was compared with Laplace wall stress. The relation of wall stress with fibrosis (picrosirius red staining) and ventricular function was analyzed. ED wall stress in all regions and RV and LV free-wall ES wall stress were increased in PAB rabbits versus sham animals. Laplace wall stress correlated well with computational models. In PAB, fibrosis was highest in the RV free wall, then septal hinge regions, and lowest in the septum and LV free wall. Fibrosis was moderately related to ED ( r = 0.47, P = 0.0011), but not ES wall stress. RV ED wall stress was strongly related to echo indexes of function (strain rate: r = 0.71, P = 0.048; E′, r = −0.75, P = 0.0077; tricuspid annular plane systolic excursion: r = 0.85, P = 0.0038) and RV fractional area change ( r = 0.77, P = 0.027). ED, more than ES, wall stress is related moderately to fibrosis and strongly to function in experimental RV pressure loading, especially at the septal hinge-point regions, where fibrosis is prominent. This suggests that wall stress partially links RV pressure loading, fibrosis, and dysfunction and may be useful to follow clinically. NEW & NOTEWORTHY Biventricular fibrosis and dysfunction impact outcomes in RV pressure loading, but their relation to wall stress is poorly defined. Using a pulmonary artery band rabbit model, we entered echocardiography and catheter data into a computer model to yield regional end-diastolic (EDWS) and end-systolic (ESWS) wall stress. EDWS, more than ESWS, correlated with fibrosis and dysfunction, especially at the fibrosis-intense septal hinge-point regions. Thus, wall stress may be clinically useful in linking RV pressure loading to regional fibrosis and dysfunction.
Дисертації з теми "Strongly annular function":
1
Daquila, Richard. "Strongly annular solutions to Mahler's functional equation /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487844948075255.
2
Fouchet, Karine. "Powers of Blaschke factors and products : Fourier coefficients and applications." Thesis, Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0647.
Анотація:
Dans cette thèse, nous calculons les formules asymptotiques pour n grand, des coefficients de Fourier de la puissance n ième d'un facteur de Blaschke, permettant de prolonger et d'affiner les estimations déjà existantes. Pour cela, nous utilisons des outils classiques d'analyse asymptotique: la méthode de la phase stationnaire et celle de la descente la plus raide. Puis en application, nous construisons des fonctions fortement annulaires dont les coefficients de Taylor satisfont des propriétés de sommation nous permettant de généraliser et d'affiner les résultats de D.D. Bonar, F.W. Carroll et G. Piranian (1977). En utilisant des polynômes plats, nous élaborons aussi une autre construction de telles fonctions à partir d'un théorème de E. Bombieri et J. Bourgain (2009). Par ailleurs, nous obtenons une majoration asymptotiquement exacte, pour n grand, de la suite (\widehat{B^n} (k))_{k \geq 0} des coefficients de Fourier de la puissance n ième d'un produit de Blaschke fini quelconque B, que nous appliquerons dans la dernière partie de la thèse à une question d'analyse matricielle/théorie des opérateurs, énoncée par J. J. Schäffer en 1970. Nous élaborons aussi des exemples constructifs de produits de Blaschke finis qui atteignent nos majorants. Enfin nous étudions le conditionnement de matrices T \in \mathcal{M}_n(\mathbb{C}) pour n grand, matrices dont le spectre est donné et qui agissent sur un espace de Hilbert ou de Banach, en particulier pour les matrices de Kreiss. Dans le cas banachique, nous utilisons notre majoration des \widehat{B^n}(k) pour construire des matrices de spectres donnés arbitraires réfutant la conjecture de SchäfferIn this thesis we first compute asymptotic formulas for Fourier coefficients of the n th-power of a Blaschke factor as n gets large which extend and sharpen known estimates on those coefficients. To perform this study we use standard tools of asymptotic analysis: the so-called method of the stationary phase and the method of the steepest descent. Next as an application of our asymptotic formulas we construct strongly annular functions with Taylor coefficients satisfying sharp summation properties. This allows us to generalize and sharpen results by D.D. Bonar, F.W. Carroll and G. Piranian (1977). Making use of properties of flat polynomials, we also present another construction of such functions built on a theorem by E. Bombieri and J. Bourgain (2009). In another part of the thesis we obtain sharp upper bounds as n gets large, on the sequence (\widehat{B^{n}}(k))_{k\geq0} of the Fourier coefficients of the n th-power of an arbitrary finite Blaschke product B, which we apply in the last part of the thesis to a question raised by J.J. Schäffer (1970) in matrix analysis/operator theory. We also provide constructive examples of finite Blaschke products that achieve our upper bounds. The last chapter is dedicated to the study of the condition numbers of large matrices T\in\mathcal{M}_{n}(\mathbb{C}) with given spectrum acting on a Hilbert space or on a Banach space, espacially for some specific classes of matrices, the so-called Kreiss matrices. In the Banach case, we use our upper bound on (\widehat{B^{n}}(k))_{k\geq0} where B is arbitrary to exhibit matrices with arbitrary given spectrum refuting Schäffer's conjecture
Частини книг з теми "Strongly annular function":
1
Greenland, David, and Mark Losleben. "Climate." In Structure and Function of an Alpine Ecosystem. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195117288.003.0007.
Анотація:
Climate is one of the most important determinants of biotic structure and function in the alpine. High winds and low temperatures are defining elements of this ecosystem, requiring adaptations of the alpine biota. Interaction between topography and snowcover strongly influences spatial heterogeneity of microclimate, which in turn influences and is influenced by the distribution of vegetation. For nearly 50 years investigators have used Niwot Ridge to examine and document the climate and its interaction with the biota of the alpine tundra. This chapter reviews some of the many findings of these ongoing bioclimatic investigations. Climate studies started on Niwot Ridge in October 1952 when Professor John W. Marr and his students set up a transect of climate stations across the Front Range between Boulder and the Continental Divide (Marr 1961). There were originally 16 stations in groups of four representing different slope exposures in what he defined as the Lower and Upper Montane Forest, the Subalpine Forest, and the Alpine Tundra ecosystems of the Front Range. After 1 year, the network was reduced to four stations, called Al, Bl, Cl, and Dl, which all had ridge-top locations and ranged from lower montane (Al) to high alpine (Dl). From time to time, these stations were supplemented by other stations that supported particular studies. This was especially true during the International Biological Programme years in the early 1970s when focus on work on the Saddle research site of the Ridge began. Following the establishment of Niwot Ridge and Green Lakes Valley as a Long-Term Ecological Research (LTER) site in 1980, even more intensive climatological work has been conducted. The construction of the Tundra Laboratory in August 1990 facilitated intensive winter climatological studies. Geographical locations and elevational data on most of the stations has been provided by Greenland (1989) and is also found in the LTER electronic database (http://culter.colorado.edu/). The climate of Niwot Ridge is characterized by large seasonal and annual variability with very windy and cold winters, wet springs, mild summers, and cool, dry autumns.
2
Smith, Raymond C., and William R. Fraser. "Climate Variability and Ecological Response of the Marine Ecosystem in the Western Antarctic Peninsula (WAP) Region." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0018.
Анотація:
The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula (WAP) region, which is the location of the Palmer LTER (figure 9.1), provide the opportunity to observe how climate-driven variability in the physical environment is related to changes in the marine ecosystem (Ross et al. 1996; Smith et al. 1996; Smith et al. 1999). This is a sea ice–dominated ecosystem where the annual advance and retreat of the sea ice is a major physical determinant of spatial and temporal change in its structure and function, from total annual primary production to the breeding success and survival of seabirds. Mounting evidence suggests that the earth is experiencing a period of rapid climate change, and air temperature records from the last half century confirm a statistically significant warming trend within the WAP during the past half century (King 1994; King and Harangozo 1998; Marshall and King 1998; Ross et al. 1996; Sansom 1989; Smith et al. 1996; Stark 1994; van den Broeke 1998; Weatherly et al. 1991). Air temperature–sea ice linkages appear to be very strong in the WAP region (Jacka 1990; Jacka and Budd 1991; King 1994; Smith et al. 1996; Weatherly et al. 1991), and a statistically significant anticorrelation between air temperatures and sea ice extent has been observed for this region. Consistent with this strong coupling, sea ice extent in the WAP area has trended down during this period of satellite observations, and the sea ice season has shortened. In addition, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests possible linkages among sea ice, cyclonic activity, and global teleconnections.
3
Oudin, Anna, John Andersson, Anna Sundström, Annelie Nordin Adolfsson, Daniel Oudin Åström, Rolf Adolfsson, Bertil Forsberg, and Maria Nordin. "Traffic-Related Air Pollution as a Risk Factor for Dementia: No Clear Modifying Effects of APOE ε4 in the Betula Cohort." In Advances in Alzheimer’s Disease. IOS Press, 2021. http://dx.doi.org/10.3233/aiad210029.
Анотація:
It is widely known that the apolipoprotein E (APOE) ε4 allele imposes a higher risk for Alzheimer’s disease (AD). Recent evidence suggests that exposure to air pollution is also a risk factor for AD, and results from a few studies indicate that the effect of air pollution on cognitive function and dementia is stronger in APOE ε4 carriers than in non-carriers. Air pollution and interaction with APOE ε4 on AD risk thus merits further attention. We studied dementia incidence over a 15-year period from the longitudinal Betula study in Northern Sweden. As a marker for long-term exposure to traffic-related air pollution, we used modelled annual mean nitrogen oxide levels at the residential address of the participants at start of follow-up. Nitrogen oxide correlate well with fine particulate air pollution levels in the study area. We had full data on air pollution, incidence of AD and vascular dementia (VaD), APOE ε4 carrier status, and relevant confounding factors for 1,567 participants. As expected, air pollution was rather clearly associated with dementia incidence. However, there was no evidence for a modifying effect by APOE ε4 on the association (p-value for interaction > 0.30 for both total dementia (AD+VaD) and AD). The results from this study do not imply that adverse effects of air pollution on dementia incidence is limited to, or stronger in, APOE ε4 carriers than in the total population.
4
Legeżyńska, Joanna, Claude De Broyer, and Jan Marcin Węsławski. "Invasion of the Poles." In Evolution and Biogeography, 216–46. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190637842.003.0009.
Анотація:
Polar Crustacea show high taxonomic and functional diversity and hold crucial roles within regional food webs. Despite the differences in the evolutionary history of the two Polar regions, present data suggest rather similar species richness, with over 2,250 taxa recorded in the Antarctic and over 1,930 noted in the Arctic. A longer duration of isolated evolution resulted in a high percentage of endemic species in the Antarctic, while the relatively young Arctic ecosystem, subjected to advection from adjacent seas, shows a very low level of endemism. Low temperatures and seasonal changes of food availability have a strong impact on polar crustacean life histories, resulting in their slow growth and development, extended life cycles, and reproduction well synchronized with annual peaks of primary production. Many species, Antarctic amphipods in particular, exhibit a clear tendency to attain large size. In both regions, abundant populations of pelagic grazers play a pivotal role in the transport of energy and nutrients to higher trophic levels. The sea-ice habitat unique to polar seas supports a wide range of species, with euphausiids and amphipods being the most important in terms of biomass in the Antarctic and Arctic, respectively. Deep sea fauna remains poorly studied, with new species being collected on a regular basis. Ongoing processes, namely a decline of sea-ice cover, increasing levels of ultraviolet radiation, and invasions of sub-polar species, are likely to reshape crustacean communities in both Polar regions.
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Walker, Marilyn W., and Mary E. Edwards. "Summary and Synthesis: Past and Future Changes in the Alaskan Boreal Forest." In Alaska's Changing Boreal Forest. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195154313.003.0028.
Анотація:
Historically the boreal forest has experienced major changes, and it remains a highly dynamic biome today. During cold phases of Quaternary climate cycles, forests were virtually absent from Alaska, and since the postglacial re-establishment of forests ca 13,000 years ago, there have been periods of both relative stability and rapid change (Chapter 5). Today, the Alaskan boreal forest appears to be on the brink of further significant change in composition and function triggered by recent changes that include climatic warming (Chapter 4). In this chapter, we summarize the major conclusions from earlier chapters as a basis for anticipating future trends. Alaska warmed rapidly at the end of the last glacial period, ca 15,000–13,000 years ago. Broadly speaking, climate was warmest and driest in the late glacial and early Holocene; subsequently, moisture increased, and the climate gradually cooled. These changes were associated with shifts in vegetation dominance from deciduous woodland and shrubland to white spruce and then to black spruce. The establishment of stands of fire-prone black spruce over large areas of the boreal forest 5000–6000 years ago is linked to an apparent increase in fire frequency, despite the climatic trend to cooler and moister conditions. This suggests that long-term features of the Holocene fire regime are more strongly driven by vegetation characteristics than directly by climate (Chapter 5). White spruce forests show decreased growth in response to recent warming, because warming-induced drought stress is more limiting to growth than is temperature per se (Chapters 5, 11). If these environmental controls persist, projections suggest that continued climate warming will lead to zero net annual growth and perhaps the movement of white spruce to cooler upland forest sites before the end of the twenty-first century. At the southern limit of the Alaskan boreal forest, spruce bark beetle outbreaks have decimated extensive areas of spruce forest, because warmer temperatures have reduced tree resistance to bark beetles and shortened the life cycle of the beetle from two years to one, shifting the tree-beetle interaction in favor of the insect (Chapter 9).
Тези доповідей конференцій з теми "Strongly annular function":
1
O’Connor, Jacqueline, Shweta Natarajan, Michael Malanoski, and Tim Lieuwen. "Disturbance Field Characteristics of a Transversely Excited Annular Jet." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22133.
Анотація:
This paper describes an investigation of transverse acoustic instabilities in premixed, swirl-stabilized flames. Additional measurements, beyond the scope of the current work, are described in O’Connor et al. [1]. Transverse excitation of swirling flow involves complex interactions between acoustic waves and fluid mechanic instabilities. The flame’s response to transverse acoustic excitation is a superposition of both acoustic and vortical disturbances that fluctuate in both the longitudinal and transverse direction. In the nozzle near field region, the disturbance field is a complex superposition of convecting vortical disturbances, as well as longer wavelength transverse and longitudinal acoustic disturbances. Farther downstream, the disturbance field is dominated by the transverse acoustic field. The phasing between the disturbances on the inside and outside of the burner annulus, as well as the left and right sides of the burner annulus is a strong function of the transverse disturbance field characteristics. For cases where the burner centerline is an approximate pressure node and velocity anti-node, the mass flow out of the left and right sides of the burner actually oscillates out-of-phase with respect to each other. In contrast, for cases where the centerline is a pressure anti-node, the burner responds symmetrically about the burner and annulus centerlines. These results show that the burner response characteristics strongly depend upon their location in the acoustic mode shape.
2
Goharzadeh, Afshin, and Peter Rodgers. "Experimental Measurement of Laminar Axisymmetric Flow Through Confined Annular Geometries With Sudden Inward Expansion." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-69237.
Анотація:
In this paper separated and reattaching laminar flows produced by a sudden inward expansion within confined annular geometries are experimentally studied. Using Particle Image Velocimetry (PIV), combined with refractive index matching, the structure of fluid flow at the expansion region was investigated. Detailed measurement of the velocities, the reattachment length (Lr) and the relative eddy intensity (ξ) are obtained for two different expansion ratios of ε = 1.4 and 1.6. The measured variation of the reattachment length as a function of Reynolds number (50 < Re < 600) was found to be non-linear for these expansion ratios. Eddy intensity was found to depend strongly on both Reynolds number and expansion ratio, with the relationship between ξ and Re being non-linear. Overall corresponding numerical predictions obtained by Nag & Datta [1] are in good agreement with the measurement results presented.
3
Sharma, Ratnesh K., Vahab Hassani, and Roop L. Mahajan. "Forced-Convective Condensation of Pure Steam and Ammonia-Steam Vapor Mixtures in a Shell-Tube Condenser." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1009.
Анотація:
Abstract In this paper, we present our experimental findings for the forced-convective condensation of pure steam and ammonia-steam vapor mixture in a horizontal annulus in a counter-current shell-tube condenser. Experiments with ammonia-steam mixtures were conducted for ∼ 90% ammonia concentration (by wt.) for vapor inlet mass fluxes ranging from 2 to 5 kg/m2s. The local heat transfer coefficient varied considerably along the condenser and this variation was strongly linked to the condensate flow patterns in the annulus. Based on a condensate drainage model, the flow in the annulus was mapped on to flow maps for horizontal in-tube condensing flows. The delineated flow regimes were utilized to explain augmentation or deterioration of local heat transfer in the condenser. The average heat transfer coefficients are presented as a function of the condensate and vapor Reynolds number for both steam and ammonia-steam mixture. The results for pure steam are higher than those predicted by annular flow correlation developed in the past. For ammonia-steam mixtures, the average heat transfer coefficients are about 16% of those for pure steam due to the vapor layer resistance at the interface.
4
Krückels, J., J. F. Mayer, and H. Stetter. "Simulation of Diffuser Flow Using an Euler Solver With a Distributed Loss Model." In ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-257.
Анотація:
The flow inside a diffuser which serves as outlet of the last turbine stage is strongly influenced by the tip leakage jet of the last blade row. For the computation of diffuser flow a quasi 3D Euler solver with a simple model for the approximation of viscous effects was developed. A body force which is calculated as a function of velocity gradients normal to the streamwise direction is included in the Euler equations. Computational cost for calculations using this method remains low, permitting its use as a design tool for turbine diffusers. Comparison of numerical results with experimental data for an annular axial radial diffuser at the outlet of a steam turbine model is presented. Flowfields for different tip clearances show a strong dependence of the pressure recovery on the tip leakage jet. Numerical results agree well with measurements.
5
Migliorini, Patrick J., Alexandrina Untaroiu, and Houston G. Wood. "A Numerical Study on the Influence of Hole Aspect Ratio on the Performance Characteristics of a Hole-Pattern Seal." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26581.
Анотація:
In turbomachinery, annular seals are used to reduce leakage between regions of high and low pressure. Many configurations of annular seals have been developed and studied in the literature including plain, labyrinth, pocket-damper, honeycomb, and hole-pattern. In machines experiencing stability issues, honeycomb and hole-pattern type seals have been used to replace labyrinth seals. Bulk-flow models are typically used to predict the leakage and dynamic coefficients of hole-pattern seals, relying on empirically derived friction factor coefficients. Previous experimental studies have shown that, for hole-pattern seals, the leakage and stator friction factor are strongly influenced by hole-depth. However, this behavior is not a monotonic function of hole-depth, a fact that might reduce confidence in future bulk-flow model predictions if not properly accounted for. A recent numerical study has highlighted the role of vortex formation in the holes which has a strong influence on the flow in the clearance region. Depending on the shape of the vortex, the flow in the hole can act much like a pinch valve, reducing the effective clearance of the jet flow. In this paper, computational fluid dynamics simulations of several hole-pattern seal configurations have been performed to study the effect of hole-aspect ratio (depth versus diameter) on the leakage and friction factors. The Reynolds Averaged Navier Stokes (RANS) equations with k-ε turbulence model were solved using ANSYS CFX. It was found that the shape of the hole influences the vortex formation within the hole, effecting the jet flow in the clearance region and the seal leakage. The results show that the leakage is heavily dependent on the hole diameter in addition to the hole depth. The relationship between the friction factors and the geometry of the seal was found to be non-monotonic. It is therefore difficult to develop a friction factor model that will accurately encompass all configurations and it is recommended that friction factor data be interpolated from experimental or numerical results.
6
Obi, Chinemerem Edmond, Yusuf Falola, Kaushik Manikonda, Abu Rashid Hasan, and Mohammad Azizur Rahman. "A Machine Learning Analysis to Relate Flow Pattern and Pressure Gradient During Gas Kicks Under Static Conditions." In SPE Western Regional Meeting. SPE, 2022. http://dx.doi.org/10.2118/209333-ms.
Анотація:
Abstract Warning signs of possible kick during drilling operation can either be primary (flow rate increase and pit gain) or secondary (drilling break, pump pressure decrease,). Drillers rely on pressure data at the surface to determine in-situ downhole conditions while drilling. The surface pressure reading is always available and accessible. However, understanding or interpretation of this data is often ambiguous. This study analyses significant kick symptoms in the wellbore annulus while under shut-in conditions. We have tied several observed annular flow patterns to the measured pressure gradient during water- air, and water-carbon dioxide complex flow. This is based on experiments in a 140-ft high flow loop, with a hydraulic diameter of approximately 3 in. The experiments were carried out under static conditions to simulate kick occurrence when the drilling fluid is not flowing, typically the wellbore is shut-in. We used an Artificial Neural Network (ANN) and K-Means clustering approach for kick prognosis. We trained these Machine learning models to detect kick symptoms from pressure response and gas evolution data collected between the kick occurrence and the Wellhead. The Artificial Neural Network (ANN) approach was relatively fast with a negligible difference in accuracy when compared for air influx and carbon dioxide influx for kick prognosis. The ANN resulted in an accuracy of about 90% and 93% for air-based kick prognosis. While the accuracy was 92% and 94% for carbon dioxide-based influx. With K-mean clustering, the Silhouette score were 0.5 and 0.6 for the air and carbon dioxide influx respectively. The estimation of the influx size and type is strongly a function of the duration of kick and bottom hole underbalanced pressure. Based on visual analysis, pit gain, and pressure signals, the quantity of the mass influx significantly controls the flow pattern, pressure losses, and pressure gradient as the kick migrates to the surface. The resulting turbulent flow after the initial kick (After Taylor bubble flow) varied with duration of kick, average liquid flow rate, influx type, and drilling scenario. We have tied the surface pressure readings to the flow regimes to better visualize well control approach while drilling. This is based on relating the significant kick symptoms we observed to the pressure readings at multiple locations and time, then training the Deep learning models based on this data. Although computationally demanding, the Deep-Learning model can use the surface pressure data to relay annular flow patterns while drilling. This work provides an alternative and relatively accessible primary kick detection tool for drillers based on measured pressure responses at the surface.
7
O’Hern, Timothy J., John R. Torczynski, Jonathan R. Clausen, and Timothy P. Koehler. "Gas-Induced Motion of an Object in a Liquid-Filled Housing During Vibration: Part II — Experiments." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69023.
Анотація:
We develop an idealized experimental system for studying how a small amount of gas can cause large net (rectified) motion of an object in a vibrated liquid-filled housing when the drag on the object depends strongly on its position. Its components include a cylindrical housing, a cylindrical piston fitting closely within this housing, a spring suspension that supports the piston, a post penetrating partway through a hole through the piston (which produces the position-dependent drag), and compressible bellows at both ends of the housing (which are well characterized surrogates for gas regions). In this system, liquid can flow from the bottom to the top of the piston and vice versa through the thin annular gaps between the hole and the post (the inner gap) and between the housing and the piston (the outer gap). When the bellows are absent, the piston motion is highly damped because small piston velocities produce large liquid velocities and large pressure drops in the Poiseuille flows within these narrow gaps. However, when the bellows are present, the piston, the liquid, and the bellows execute a collective motion called the Couette mode in which almost no liquid is forced through the gaps. Since its damping is low, the Couette mode has a strong resonance. Near this frequency, the piston motion becomes large, and the nonlinearity associated with the position-dependent drag of the inner gap produces a net (rectified) force on the piston that can cause it to move downward against its spring suspension. Experiments are performed using two variants of this system. In the single-spring setup, the piston is pushed up against a stop by its lower supporting spring. In the two-spring setup, the piston is suspended between upper and lower springs. The equilibrium piston position is measured as a function of the vibration frequency and acceleration, and these results are compared to corresponding analytical results (Torczynski et al., 2017). A quantitative understanding of the nonlinear behavior of this system may enable the development of novel tunable dampers for sensing vibrations of specified amplitudes and frequencies.
8
Balasubramanian, P., and D. A. Edwards. "Efficient Realization of Strongly Indicating Function Blocks." In 2008 IEEE Computer Society Annual Symposium on VLSI. IEEE, 2008. http://dx.doi.org/10.1109/isvlsi.2008.103.
9
Abdel-Raouf, Emad, John Baker, and Muhammad Sharif. "The Effects of Blocking Ratio and Atmospheric Altitude on Starting Annular Jets." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30767.
Анотація:
The effects of the blocking ratio and atmospheric altitude on starting annular air jets at a low Reynolds number are investigated by examining the velocity profiles, jet entrainment and vortex formation. A 2D axisymmetric numerical model is developed to perform the analysis. The numerical model is validated with theoretical and experimental results from other studies. In order to achieve a comprehensive analysis, the annular jet is tested for blocking ratios with the values of 0.00 (i.e. a round jet), 0.50 and 0.75. Air properties at altitudes of 0.00 km, 18.90 km and 33.75 km are tested to simulate atmospheric environments at sea level, edge of near space and near space, respectively. The results showed that the starting jet velocity profile, entrainment and vortex formation is a strong function of blocking ratio. On the other hand, the same parameters are shown to be nearly independent, strong and weak functions of atmospheric altitude, respectively.
10
Bass, Elisa C., and Jeffrey C. Lotz. "A Strain Energy Function for the Annulus Fibrosus Specified Using Biaxial Experimental Data." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0457.
Анотація:
Abstract The mechanical behavior of the annulus fibrosus has typically been characterized through the use of uniaxial tests. In contrast, its in vivo constraints are multiaxial and likely result in a mechanical response very different from that observed to date in vitro. The goal of this study was to test the annulus in biaxial tension and use these data to determine an elastic strain energy function for the annulus. Our results demonstrate that the mechanical response of the annulus is dramatically influenced by a biaxial constraint, and that these experiments provide important data for the determination of the constitutive formulation for this strongly anisotropic and nonlinear tissue.
Звіти організацій з теми "Strongly annular function":
1
Arora, Sanjana, and Olena Koval. Norway Country Report. University of Stavanger, 2022. http://dx.doi.org/10.31265/usps.232.
Анотація:
This report is part of a larger cross-country comparative project and constitutes an account and analysis of the measures comprising the Norwegian national response to the COVID-19 pandemic during the year of 2020. This time period is interesting in that mitigation efforts were predominantly of a non-medical nature. Mass vaccinations were in Norway conducted in early 2021. With one of the lowest mortality rates in Europe and relatively lower economic repercussions compared to its Nordic neighbours, the Norwegian case stands unique (OECD, 2021: Eurostat 2021; Statista, 2022). This report presents a summary of Norwegian response to the COVID-19 pandemic by taking into account its governance, political administration and societal context. In doing so, it highlights the key features of the Nordic governance model and the mitigation measures that attributed to its success, as well as some facets of Norway’s under-preparedness. Norway’s relative isolation in Northern Europe coupled with low population density gave it a geographical advantage in ensuring a slower spread of the virus. However, the spread of infection was also uneven, which meant that infection rates were concentrated more in some areas than in others. On the fiscal front, the affluence of Norway is linked to its petroleum industry and the related Norwegian Sovereign Wealth Fund. Both were affected by the pandemic, reflected through a reduction in the country’s annual GDP (SSB, 2022). The Nordic model of extensive welfare services, economic measures, a strong healthcare system with goals of equity and a high trust society, indeed ensured a strong shield against the impact of the COVID-19 pandemic. Yet, the consequences of the pandemic were uneven with unemployment especially high among those with low education and/or in low-income professions, as well as among immigrants (NOU, 2022:5). The social and psychological effects were also uneven, with children and elderly being left particularly vulnerable (Christensen, 2021). Further, the pandemic also at times led to unprecedented pressure on some intensive care units (OECD, 2021). Central to handling the COVID-19 pandemic in Norway were the three national executive authorities: the Ministry of Health and Care services, the National directorate of health and the Norwegian Institute of Public Health. With regard to political-administrative functions, the principle of subsidiarity (decentralisation) and responsibility meant that local governments had a high degree of autonomy in implementing infection control measures. Risk communication was thus also relatively decentralised, depending on the local outbreak situations. While decentralisation likely gave flexibility, ability to improvise in a crisis and utilise the municipalities’ knowledge of local contexts, it also brought forward challenges of coordination between the national and municipal level. Lack of training, infection control and protection equipment thereby prevailed in several municipalities. Although in effect for limited periods of time, the Corona Act, which allowed for fairly severe restrictions, received mixed responses in the public sphere. Critical perceptions towards the Corona Act were not seen as a surprise, considering that Norwegian society has traditionally relied on its ‘dugnadskultur’ – a culture of voluntary contributions in the spirit of solidarity. Government representatives at the frontline of communication were also open about the degree of uncertainty coupled with considerable potential for great societal damage. Overall, the mitigation policy in Norway was successful in keeping the overall infection rates and mortality low, albeit with a few societal and political-administrative challenges. The case of Norway is thus indeed exemplary with regard to its effective mitigation measures and strong government support to mitigate the impact of those measures. However, it also goes to show how a country with good crisis preparedness systems, governance and a comprehensive welfare system was also left somewhat underprepared by the devastating consequences of the pandemic.