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Artykuły w czasopismach na temat "High Weissenberg number problem"
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Keunings, Roland. "On the high Weissenberg number problem". Journal of Non-Newtonian Fluid Mechanics 20 (styczeń 1986): 209–26. http://dx.doi.org/10.1016/0377-0257(86)80022-2.
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Trebotich, David. "Toward a solution to the high Weissenberg number problem". PAMM 7, nr 1 (grudzień 2007): 2100073–74. http://dx.doi.org/10.1002/pamm.200700989.
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Evans, J. D. "Re-entrant corner flows of upper convected Maxwell fluids: the small and high Weissenberg number limits". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 462, nr 2076 (21.07.2006): 3749–74. http://dx.doi.org/10.1098/rspa.2006.1737.
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We discuss here the steady planar flow of the upper convected Maxwell fluid at re-entrant corners in the singular limits of small and large Weissenberg number. The Weissenberg number is a parameter representing the dimensionless relaxation time and hence the elasticity of the fluid. Its value determines the strength of the fluid memory and thus the influence of elastic effects over viscosity. The small Weissenberg limit is that in which the elastic effects are small and the fluid's memory is weak. It is an extremely singular limit in which the behaviour of a Newtonian fluid is obtained in a main core region away from the corner and walls. Elastic effects are confined to boundary layers at the walls and core regions nearer to the corner. The actual asymptotic structure comprises a complicated four-region structure. The other limit of interest is the large Weissenberg limit (or high Weissenberg number problem) in which the elastic effects now dominate in the main regions of the flow. We explain how the transition in solution from Weissenberg order 1 flows to high Weissenberg flows is achieved, with the singularity in the stress field at the corner remaining the same but its effects now extending over larger length-scales. Implicit in this analysis is the absence of a lip vortex. We also show (for the main core region) that there is a small reduction in the velocity field at the corner and walls where it becomes smoother. This high Weissenberg number limit has a six-region local asymptotic structure and comment is made on its relevance to the case in which a lip vortex is present.
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Mohamadali, Meysam, i Nariman Ashrafi. "Similarity Solution for High Weissenberg Number Flow of Upper-Convected Maxwell Fluid on a Linearly Stretching Sheet". Journal of Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/9718786.
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High Weissenberg boundary layer flow of viscoelastic fluids on a stretching surface has been studied. The flow is considered to be steady, low inertial, and two-dimensional. Upon proper scaling and by means of an exact similarity transformation, the nonlinear momentum and constitutive equations of each layer transform into the respective system of highly nonlinear and coupled ordinary differential equations. Numerical solutions to the resulting boundary value problem are obtained using an efficient shooting technique in conjunction with a variable stepping method for different values of pressure gradients. It is observed that, unlike the Newtonian flows, in order to maintain a potential flow, normal stresses must inevitably develop. The velocity field and stresses distributions over plate are presented for difference values of pressure gradient and Weissenberg numbers.
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TANOUE, Shuichi, Jiro KOGA, Toshihisa KAJIWARA, Yoshiyuki IEMOTO i Kazumori FUNATSU. "High Weissenberg Number Problem and Numerical Simulation of an Annular Extrudate Swell of Viscoelastic Fluids." Seikei-Kakou 9, nr 10 (1997): 817–24. http://dx.doi.org/10.4325/seikeikakou.9.817.
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Bielça Silva, Luciene Aparecida, i Messias Meneguette. "Log-Conformation Representation of Hiperbolic Conservation Laws with Source Term". TEMA (São Carlos) 15, nr 3 (27.01.2014): 293. http://dx.doi.org/10.5540/tema.2014.015.03.0293.
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<pre>The objective of this work is to study, through a simpler equation, the statement that the numerical instability associated to the high number of Weissenberg in equations with source term can be resolved by the use of the so called logarithmic representation conformation. We will focus on hyperbolic conservation laws, but more specifically on the advection equation with source term. The source term imposes a necessity of an elastic balance, as well as the CFL convective balance for stability. We will see that the representation of such equation by log-conformation removes the restriction of stability inherent to the elastic balance pointed out by [3] as the cause of high Weissenberg number problem (HWNP).</pre>
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Renardy, Michael. "The initial value problem for creeping flow of the upper convected Maxwell fluid at high Weissenberg number". Mathematical Methods in the Applied Sciences 38, nr 5 (17.03.2014): 959–65. http://dx.doi.org/10.1002/mma.3121.
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Varchanis, S., A. Syrakos, Y. Dimakopoulos i J. Tsamopoulos. "A new finite element formulation for viscoelastic flows: Circumventing simultaneously the LBB condition and the high-Weissenberg number problem". Journal of Non-Newtonian Fluid Mechanics 267 (maj 2019): 78–97. http://dx.doi.org/10.1016/j.jnnfm.2019.04.003.
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Abedijaberi, A., i B. Khomami. "Continuum and multi-scale simulation of mixed kinematics polymeric flows with stagnation points: Closure approximation and the high Weissenberg number problem". Journal of Non-Newtonian Fluid Mechanics 166, nr 11 (czerwiec 2011): 533–45. http://dx.doi.org/10.1016/j.jnnfm.2011.03.001.
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AFONSO, A. M., P. J. OLIVEIRA, F. T. PINHO i M. A. ALVES. "Dynamics of high-Deborah-number entry flows: a numerical study". Journal of Fluid Mechanics 677 (13.04.2011): 272–304. http://dx.doi.org/10.1017/jfm.2011.84.
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High-elasticity simulations of flows through a two-dimensional (2D) 4 : 1 abrupt contraction and a 4 : 1 three-dimensional square–square abrupt contraction were performed with a finite-volume method implementing the log-conformation formulation, proposed by Fattal & Kupferman (J. Non-Newtonian Fluid Mech., vol. 123, 2004, p. 281) to alleviate the high-Weissenberg-number problem. For the 2D simulations of Boger fluids, modelled by the Oldroyd-B constitutive equation, local flow unsteadiness appears at a relatively low Deborah number (De) of 2.5. Predictions at higher De were possible only with the log-conformation technique and showed that the periodic unsteadiness grows with De leading to an asymmetric flow with alternate back-shedding of vorticity from pulsating upstream recirculating eddies. This is accompanied by a frequency doubling mechanism deteriorating to a chaotic regime at high De. The log-conformation technique provides solutions of accuracy similar to the thoroughly tested standard finite-volume method under steady flow conditions and the onset of a time-dependent solution occurred approximately at the same Deborah number for both formulations. Nevertheless, for Deborah numbers higher than the critical Deborah number, and for which the standard iterative technique diverges, the log-conformation technique continues to provide stable solutions up to quite (impressively) high Deborah numbers, demonstrating its advantages relative to the standard methodology. For the 3D contraction, calculations were restricted to steady flows of Oldroyd-B and Phan-Thien–Tanner (PTT) fluids and very high De were attained (De ≈ 20 for PTT with ϵ = 0.02 and De ≈ 10000 for PTT with ϵ = 0.25), with prediction of strong vortex enhancement. For the Boger fluid calculations, there was inversion of the secondary flow at high De, as observed experimentally by Sousa et al. (J. Non-Newtonian Fluid Mech., vol. 160, 2009, p. 122).
Rozprawy doktorskie na temat "High Weissenberg number problem"
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Wang, Xiaojun. "Well-posedness results for a class of complex flow problems in the high Weissenberg number limit". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/27669.
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For simple fluids, or Newtonian fluids, the study of the Navier-Stokes equations in the high Reynolds number limit brings about two fundamental research subjects, the Euler equations and the Prandtl's system. The consideration of infinite Reynolds number reduces the Navier-Stokes equations to the Euler equations, both of which are dealing with the entire flow region. Prandtl's system consists of the governing equations of the boundary layer, a thin layer formed at the wall boundary where viscosity cannot be neglected.
In this dissertation, we investigate the upper convected Maxwell(UCM) model for complex fluids, or non-Newtonian fluids, in the high Weissenberg number limit. This is analogous to the Newtonian fluids in the high Reynolds number limit. We present two well-posedness results.
The first result is on an initial-boundary value problem for incompressible hypoelastic materials which arise as a high Weissenberg number limit of viscoelastic fluids. We first assume the stress tensor is rank-one and develop energy estimates to show the problem is locally well-posed. Then we show the more general case can be handled in the same spirit. This problem is closely related to the incompressible ideal magneto-hydrodynamics (MHD) system.
The second result addresses the formulation of a time-dependent elastic boundary layer through scaling analysis. We show the well-posedness of this boundary layer by transforming to Lagrangian coordinates. In contrast to the possible ill-posedness of Prandtl's system in Newtonian fluids, we prove that in non-Newtonian fluids the stress boundary layer problem is well-posed.Ph. D.
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Niethammer, Matthias Samuel [Verfasser]. "A Finite Volume Framework for Viscoelastic Flows at High Weissenberg Number / Matthias Samuel Niethammer". München : Verlag Dr. Hut, 2019. http://d-nb.info/1190421909/34.
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Souccar, Adham W. "Heat Transfer and Mass Transfer with Heat Generation in Drops at High Peclet Number". University of Toledo / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177603981.
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Dey, Anita Anup. "Experimental Study on Viscoelastic Fluid-Structure Interactions". 2017. https://scholarworks.umass.edu/masters_theses_2/502.
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It is well known that when a flexible or flexibly-mounted structure is placed perpendicular to the flow of a Newtonian fluid, it can oscillate due to the shedding of separated vortices at high Reynolds numbers. If the same flexible object is placed in non-Newtonian flows, however, the structure's response is still unknown. The main objective of this thesis is to introduce a new field of viscoelastic fluid-structure interactions by showing that the elastic instabilities that occur in the flow of viscoelastic fluids can drive the motion of a flexible structure placed in its path. Unlike Newtonian fluids, the flow of viscoelastic fluids can become unstable at infinitesimal Reynolds numbers due to the onset of a purely elastic flow instability. This instability occurs in the absence of nonlinear effects of fluid inertia and the Reynolds number of the flows studied here are in the order of 10-4. When such an elastic flow instability occurs in the vicinity of a flexible structure, the fluctuating fluid forces exerted on the structure grow large enough to cause a structural instability which in turn feeds back into the fluid resulting in a flow instability. Nonlinear periodic oscillations of the flexible structure are observed which have been found to be coupled to the time-dependent growth and decay of viscoelastic stresses in the wake of the structure. Presented in this thesis are the results of an investigation of the interaction occurring in the flow of a viscoelastic wormlike micelle solution past a flexible rectangular sheet. The structural geometries studied include: flexible sheet inclinations at 20°, 45° and 90° and flexible sheet widths of 5mm and 2.5mm. By varying the flow velocity, the response of the flexible sheet has been characterized in terms of amplitude and frequency of oscillations. Steady and dynamic shear rheology and filament stretching extensional rheology measurements are conducted in order to characterize the viscoelastic wormlike micelle solution. Bright field images show the deformation of the flexible sheet during an unstable oscillation while flow-induced birefringence images highlight the viscoleastic fluid stresses produced in the wake of the flexible sheet.
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Arun, Dalal Swapnil. "A Numerical Study of Droplet Dynamics in Viscoelastic Flows". Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2702.
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The polymers are integral part of vast number of products used in day to day life due to their anomalous viscoelastic behaviour. The remarkable flow behaviour exhibited by the polymeric fluids including rod climbing, extrudate swell, tube-less siphon, viscoelastic jet, elastic recoil and sharkskin instability is attributed to the complex microstructures in the polymeric liquids that arise due to the interactions of long chain polymer molecules with each other and with the surrounding fluid particles. The significance of polymer in transportation, packaging, pharmaceutical, chemical, biomedical, textiles, food and polymer processing industries highlights the requirement to comprehend the complex rheology of polymeric fluids.
First, we investigate the flow features exhibited by different shear thinning vis-coelastic fluids in rectangular cavities over a wide range of depth to width ratio. We have developed a viscoelastic flow solver in order to perform numerical simulations of highly elastic flow of viscoelastic fluids. In particular, we discuss the simulations of flows of constant viscosity Boger and shear thinning viscoelastic fluids in the complex flow problems using different constitutive equations. The effects of elasticity and inertia on the flow behaviour of two shear thinning vis-coelastic fluids modeled using Giesekus and linear PTT constitutive equations in rectangular cavities is studied. The size of the primary eddies and critical aspect ratio over which the corner eddies merge to yield a second primary eddy in deep cavities is discussed. We demonstrate that the flow in the shallow and deep cavities can be characterized using Weissenberg number, defined based on the shear rate, and Deborah number, specified based on the convective time scale, respectively. The study of flow in driven cavities is important in understanding of the mixing process during synthesis of blends and composites.
Next, we study two phase polymeric flow in confined geometries. Nowadays, polymer processing industries prefer to develop newer polymer with the desired material properties mechanically by mixing and blending of different polymer components instead of chemically synthesizing fresh polymer. The microstructure of blends and emulsions following drop deformation, breakup and coalescence during mixing determines its macroscopic interfacial rheology. We developed a two phase viscoelastic flow solver using volume conserving sharp interface volume-of-fluid (VOF) method for studying the dynamics of single droplet subjected to the complex flow fields.
We investigated the effects of drop and matrix viscoelasticity on the motion and deformation of a droplet suspended in a fully developed channel flow. The flow behaviour exhibited by Newtonian-Newtonian, viscoelastic-Newtonian, Newtonian-viscoelastic and viscoelastic-viscoelastic drop-matrix systems is presented. The difference in the drop dynamics due to presence of constant viscosity Boger fluid and shear thinning viscoelastic fluid is represented using FENE-CR and linear PTT constitutive equations, respectively. The presence of shear thinning viscoelastic fluid either in the drop or the matrix phase suppresses the drop deformation due to stronger influence of matrix viscoelasticity as compared to the drop elasticity. The shear thinning viscoelastic drop-matrix system further restricts the drop deformation and it displays non-monotonic de-formation. The constant viscosity Boger fluid droplet curbs the drop deformation and exhibits flow dynamics identical to the shear thinning viscoelastic droplet, thus indicating that the nature of the drop viscoelasticity has little influence on the flow behaviour. The matrix viscoelasticity due to Boger fluid increases drop deformation and displays non-monotonic deformation. The drop deformation is further enhanced in the case of Boger fluid in viscoelastic drop-matrix system. Interestingly, the pressure drop due to the presence of viscoelastic drop in a Newtonian matrix is lower than the single phase flow of Newtonian fluid. We also discuss the effects of inertia, surface tension, drop to matrix viscosity ratio and the drop size on these drop-matrix systems.
Finally, we investigate the emulsion rheology by studying the motion of a droplet in the square lid driven cavity flow. The viscoelastic effects due to constant viscosity Boger fluid and shear thinning viscoelastic fluid are illustrated using FENECR and Giesekus rheological relations, respectively. The presence of viscoelasticity either in drop or matrix phase boosts the drop deformation with the drop viscoelasticity displaying intense deformation. The drop dynamics due to the droplet viscoelasticity is observed to be independent of the nature of vis-coelastic fluid. The shear thinning viscoelastic matrix has a stronger influence on the drop deformation and orientation compared to the Boger fluid matrix. The different blood components, cells and many materials of industrial importance are viscoelastic in nature. Thus, the present study has significant applications in medical diagnostics, drug delivery, manufacturing and processing industries, study of biological flows, pharmaceutical research and development of lab-on-chip devices.
Książki na temat "High Weissenberg number problem"
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Fridman, Yuriy, i Aleksandr Korzhenevich. Learning to solve problems in physics: preparing for the Unified State Exam. ru: INFRA-M Academic Publishing LLC., 2021. http://dx.doi.org/10.12737/995926.
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If you are holding this textbook in your hands, it means that you understand the need to solve problems when studying a physics course at school. Indeed, it is difficult to overestimate the effect that the solution of problems in the study of physics gives. The textbook contains about 800 problems for the high school physics course. The tasks are based on the examination materials of various universities, including the Republic of Crimea, data from the magazines "Kvant", "Physics at School", information received from correspondence physics and mathematics schools of the Moscow State University named after M. V. Lomonosov, National Research Nuclear University "MEPhI", Bauman Moscow State Technical University, Moscow Institute of Physics and Technology (State University). We also used the problem books that were released in various years to help those entering universities. The number of problems and their selection are not random and allow, according to the compilers, to demonstrate the types of problems that are often found in the high school physics course, the most rational methods, general approaches and ideas for solving them, and also help to acquire certain skills in solving problems. Can be useful for use in secondary schools when working with students for whom physics is of interest, optional, if you prepare for the entrance exams for physics, a specialized school with advanced study of physics, as well as anyone who wants to learn how to solve problems in physics.
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Federighi, Paolo, i Francesca Torlone, red. Low skilled take their qualifications "one step up". Florence: Firenze University Press, 2010. http://dx.doi.org/10.36253/978-88-6453-179-3.
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Adult learning is recognized as a key component of lifelong learning and Member States are required to remove barriers to participation, to increase overall quality and efficiency in adult learning, to speed up the process of validation and recognition and to ensure sufficient investment in and monitoring of the field (European Commission, 2006, 2007; European Parliament, 2008; European Council, 2008). It is unanimously recognized that adult learning can play a pivotal role in meeting the goals of the Lisbon Strategy, by fostering social cohesion, providing citizens with the skills required to find new jobs and helping Europe to better respond to the challenges of globalisation. Such needs are taken into consideration in this Volume where the main issues faced are related to what 33 European countries have been doing in order to raise the skills levels of low-skilled workers, address the problem of the high number of early school leavers, combat social exclusion, ensure the efficiency, effectiveness, quality of adult learning.
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Homenko, Elena. Legal regulation of the digital national payment system of the Russian Federation. ru: INFRA-M Academic Publishing LLC., 2022. http://dx.doi.org/10.12737/1905572.
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The textbook is devoted to a currently relevant problem — the analysis of digital transformations in the modern national payment system and payment systems as its structural elements. The textbook reveals the features of the construction of the NPS of Russia, the range of its subjects, the relationship with the banking system of our state and the banking systems of a number of foreign countries. The features of the functioning of the payment system of the Bank of Russia are analyzed, its high importance in the field of settlements is shown
, taking into account the new digital technologies being introduced. The advantages of using modern technologies and tools are highlighted, as well as the associated new serious risks affecting the interests of consumers of payment services, including individuals.
For students of the master's degree level, postgraduates, teachers of law and economics universities and faculties, entrepreneurs and practicing lawyers, as well as for anyone interested in the specifics of building the NPS of Russia in the conditions of digitalization.
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O’Flaherty, Martin, Susanna Sans-Menendez, Simon Capewell i Torben Jørgensen. Epidemiology of atherosclerotic cardiovascular disease: scope of the problem and its determinants. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199656653.003.0001.
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The epidemic of cardiovascular disease (CVD) in the twentieth century prompted many population-based surveys. Now, a huge number of epidemiological studies provide a clear picture of the risk for CVD. Approximately 80% of CVD can be explained by smoking, high blood pressure, and deterioration of lipid and glucose metabolism, the two latter mediated through an unhealthy diet (high intake of salt, saturated fat, and refined sugar) and physical inactivity. A causal web for CVD shows that the influence is seen throughout the life course, and that ‘upstream‘ factors like socioeconomic status, health policies, and industrial influences all have a powerful impact on the more downstream parameters like lifestyle and biomarkers. This emphasizes that population-level interventions represent the most effective options for future strategies for the prevention of CVD.
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Riley, Barry. Change . . . and Resisting Change. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190228873.003.0022.
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The combination of ongoing U.S. budget stringency and continually increasing prices for food globally means that the size of traditional food aid shipments has been dropping. But so, too, has the number of food-insecure people. Is the need for food aid also declining? The number of refugees and conflict-displaced people is at an all-time high. In absolute numbers the food security situation in Sub-Saharan Africa is not improving. Continued high population growth and a slowing of progress in agricultural yields in that continent may mean that the hunger problem may well increase rather than decrease over the next fifty years. A continuation of global warming trends seems likely to further retard yields of unirrigated food crops and increase food prices in poor countries. Can the experience of the past 220 years of American responses to hunger abroad inform America’s responses in the decades ahead?
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Ashton, David, Caroline Lloyd i Chris Warhurst. Business Strategies and Skills. Redaktorzy John Buchanan, David Finegold, Ken Mayhew i Chris Warhurst. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199655366.013.15.
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This chapter examines the link between business strategies and skill in the context of the the latter being regarded as key to economic growth and competitive advantage. A high-skilled workforce is viewed both as a driver of this approach and one of its outcomes. A number of countries have attempted to create more high-skilled jobs through raising the qualification levels of their workforces. The idea behind this supply-side intervention is that a high-skilled workforce will attract businesses that wish to or already do compete on quality and/or innovation or will encourage existing organisations to make better use of these skills and improve organisational performance. The problem is increasing evidence of growing levels of over-qualification amongst these workforces as too few high skilled jobs are created. Moreover many firms have remained successful operating with low skilled jobs competing on cost. Drawing on existing research, this chapter explores these developments and issues. It starts by making an important contextual distinction between skill levels and skill use, how they feature in firm business strategies, and their relevance to governments, employers and employees. It then presents the two key theories of skill and business strategies: the HRM Approach and the Institutional/Comparative Approaches. Questioning the determinism of these approaches, the chapter then seeks to move debate beyond assumptions of direct relationships between strategy and skill. The conclusion presents an alternative approach to developing the relationship between business strategies and skill that incorporates managerial agency.
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Ruban, Anatoly I. Trailing-Edge Flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199681754.003.0004.
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Chapter 3 focuses on the high-Reynolds number flow of an incompressible fluid near the trailing edge of a flat plate. It begins with Goldstein’s (1930) solution for a viscous wake behind the plate, and shows that the displacement effect of the wake produces a singular pressure gradient near the trailing edge. It further shows that this singularity leads to a formation triple-deck viscous-inviscid interaction region that occupies a small vicinity of the trailing edge. A detailed analysis of the flow in each tier of the triple-deck structure is conducted based on the asymptotic analysis of the Navier–Stokes equations. As a result, the so-called ‘interaction problem’ is formulated. It concludes with the numerical solution of so-called ‘interaction problem’.
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Cheng, Russell. Finite Mixture Models. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198505044.003.0017.
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Fitting a finite mixture model when the number of components, k, is unknown can be carried out using the maximum likelihood (ML) method though it is non-standard. Two well-known Bayesian Markov chain Monte Carlo (MCMC) methods are reviewed and compared with ML: the reversible jump method and one using an approximating Dirichlet process. Another Bayesian method, to be called MAPIS, is examined that first obtains point estimates for the component parameters by the maximum a posteriori method for different k and then estimates posterior distributions, including that for k, using importance sampling. MAPIS is compared with ML and the MCMC methods. The MCMC methods produce multimodal posterior parameter distributions in overfitted models. This results in the posterior distribution of k being biased towards high k. It is shown that MAPIS does not suffer from this problem. A simple numerical example is discussed.
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Popovici, Ioana, i Michael T. French. Substance Use and School and Occupational Performance. Redaktor Kenneth J. Sher. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199381708.013.003.
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Health economists have been actively investigating the relationships between substance use and educational achievement/labor market performance outcomes. Although researchers agree on the direction and magnitude of the relationships between substance use and some of these outcomes, many questions remain unanswered. For instance, the literature generally indicates that drug use has a negative impact on most academic outcomes. Less evidence exists, however, of a negative impact of alcohol use on education. Although results suggest that drinking is associated with lower grades, and most research shows that drinking negatively impacts the probability of graduating from high school, several studies have been unable to find significant relationships between alcohol consumption and the number of years of schooling completed. Similarly, although most studies find a wage premium for moderate alcohol users, results on the effect of problem drinking or the use of other drugs on the probability of employment are mixed.
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Pires, Stephen F., i William D. Moreto. The Illegal Wildlife Trade. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199935383.013.161.
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The illegal wildlife trade is a growing problem driven by a number of factors (e.g. subsistence, alternative medicine, accessories, the pet trade). High demand for illicit wildlife products is threatening the existence of many of the most-endangered species. By unsustainably removing coveted species from the wild, communities that depend on such species for subsistence or eco-tourism will be adversely impacted by depleting populations. Laws and regulations have been implemented over the years, most notably CITES, to regulate the commercial trade in wildlife and prohibit trade in other species that are at-risk of overexploitation albeit with mixed success. Criminologists have recently entered the fold and provided insight to the wildlife trade through various perspectives. Researchers are beginning to better understand why and how the trade operates and what solutions might be implemented to reduce it. The article ends with implications for future research.
Części książek na temat "High Weissenberg number problem"
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Renardy, M. "High Weissenberg Number Asymptotics and Corner Singularities in Viscoelastic Flows". W IUTAM Symposium on Non–Linear Singularities in Deformation and Flow, 13–20. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4736-1_2.
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Steves, B. A., G. B. Valsecchi, E. Perozzi i A. E. Roy. "Significant High Number Commensurabilities in the Main Lunar Problem II: The Occurrence of Saros-Like Near Periodicities". W Interactions Between Physics and Dynamics of Solar System Bodies, 341–58. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1902-3_28.
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Roy, A. E., B. A. Steves, G. B. Valsecchi i E. Perozzi. "Significant High Number Commensurabilities in the Main Lunar Problem: A Postscript to a Discovery of the Ancient Chaldeans". W Predictability, Stability, and Chaos in N-Body Dynamical Systems, 273–82. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5997-5_22.
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Yamada, Susumu, Toshiyuki Imamura i Masahiko Machida. "High Performance Parallel LOBPCG Method for Large Hamiltonian Derived from Hubbard Model on Multi-GPU Systems". W Supercomputing Frontiers, 1–19. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-10419-0_1.
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AbstractThe physical property of the Hubbard model can be understood by solving the eigenvalue problem for the Hamiltonian derived from the model. Since the Hamiltonian is a large sparse matrix, an iteration method is usually utilized for solving the problems. One of effectual solvers for this problem is the LOBPCG (Locally Optimal Block Preconditioned Conjugate Gradient) method. The tuning strategies of the method on GPU systems when all iteration vectors are stored in device memory have been proposed. In this research, we propose tuning strategies for parallel LOBPCG method on multi-GPU system when the Hamiltonian is large and some iteration vectors are stored in host memory. When the LOBPCG method is used for solving multi eigenpairs (eigenvalues and the corresponding eigenvectors), the number of iteration vectors, whose size is the same as the dimension of the Hamiltonian, is proportional to the number of the eigenpairs. On the other hand, the memory consumption for the non-zero elements of the Hamiltonian can be significantly reduced by considering the regular arrangement of the elements. Therefore, when we execute the LOBPCG method for a large Hamiltonian on GPUs, some of the vectors have to be stored on host memory and have to be transferred between host and device memory as needed. Since the cost of the data transfer is very large, we also propose the optimization for it. The simulation result on a multi-GPU system shows that the optimization of the data transfer is very effective for high performance computing.
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Tang, Lihe, Weidong Yang, Qiang Gao, Rui Xu i Rongzhi Ye. "A Lightweight Verification Scheme Based on Dynamic Convolution". W Proceeding of 2021 International Conference on Wireless Communications, Networking and Applications, 778–87. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2456-9_78.
Pełny tekst źródłaStreszczenie:
AbstractSince Electricity Grid Engineering involves a large number of personnel in the construction process, face recognition algorithms can be used to solve the personnel management problem. The recognition devices used in Electricity Grid Engineering are often mobile, embedded, and other lightweight devices with limited hardware performance. Although a large number of existing face recognition algorithms based on deep convolutional neural networks have high recognition accuracy, they are difficult to run in mobile devices or offline environments due to high computational complexity. In order to maintain the accuracy of face recognition while reducing the complexity of face recognition networks, a lightweight face recognition network based on Dynamic Convolution is proposed. Based on MobileNetV2, this paper introduces the Dynamic Convolution operation. It proposes a Dynamic Inverted Residuals Block, which enables the lightweight neural network to combine the feature extraction and learning ability of large neural networks to improve the recognition accuracy of the model. The experiments prove that the proposed model maintains high recognition accuracy while ensuring lightweight.
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Consoli, Sergio, Domenico Perrotta i Marco Turchi. "Reduced Variable Neighbourhood Search for the Generation of Controlled Circular Data". W Variable Neighborhood Search, 83–98. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-69625-2_7.
Pełny tekst źródłaStreszczenie:
AbstractA number of artificial intelligence and machine learning problems need to be formulated within a directional space, where classical Euclidean geometry does not apply or needs to be readjusted into the circle. This is typical, for example, in computational linguistics and natural language processing, where language models based on Bag-of-Words, Vector Space, or Word Embedding, are largely used for tasks like document classification, information retrieval and recommendation systems, among others. In these contexts, for assessing document clustering and outliers detection applications, it is often necessary to generate data with directional properties and units that follow some model assumptions and possibly form close groups. In the following we propose a Reduced Variable Neighbourhood Search heuristic which is used to generate high-dimensional data controlled by the desired properties aimed at representing several real-world contexts. The whole problem is formulated as a non-linear continuous optimization problem, and it is shown that the proposed Reduced Variable Neighbourhood Search is able to generate high-dimensional solutions to the problem in short computational time. A comparison with the state-of-the-art local search routine used to address this problem shows the greater efficiency of the approach presented here.
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Andersson, Anna-Lena, i Kenneth Svensson. "Suicide in the Transport System". W The Vision Zero Handbook, 1103–15. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-76505-7_42.
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AbstractThe Swedish Transport Administration (STA) work to reduce the number of suicides in the transport system. Fatalities, i.e., on roads, railways, and bridges, originate from either accidents or suicides, natural death excluded. Knowing the correct manner of death is needed to work with optimal prevention strategies. The aims are to separate fatalities due to suicides, follow the development, and implement measures for suicide prevention. Methods are developed for suicide classification and criteria for the selection in which suicides were suspected. Fatalities in level one and two of five were classified as suicides. Data from the STA’s databases are used and so are data from the psychosocial investigations done by a trained investigator in the topic and with clinical experience from counselling at hospitals. 2129 persons died on the roads in Sweden, 10% (206 persons) were classified as suicides. 336 persons died after being hit by trains, 85% (284 persons) were suicides. 130 persons died by jumping from bridges.The number of suicides increases with population density. Suicide in the transport system is a major problem; firstly personal tragedies, it is also a work environment problem for truck and train drivers and for the emergency staff. It generates delays and costs for passenger and cargo transport. By analyzing the results of countermeasures in the form of obstructive barriers, the physical environment can be improved and high-risk areas can be accentuated. Restricting access to the means of suicide is important in suicide prevention. Strategies for the STA include suicide prevention in the design of new roads, railways, and bridges, as well as by identifying and reducing existing high-risk locations. Sharing the results with other authorities and organizations and cooperation within suicide prevention missions are vital for the enhancement of the overall suicide prevention work in society.
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Andersson, Anna-Lena, i Kenneth Svensson. "Suicide in the Transport System". W The Vision Zero Handbook, 1–13. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-23176-7_42-2.
Pełny tekst źródłaStreszczenie:
AbstractThe Swedish Transport Administration (STA) work to reduce the number of suicides in the transport system. Fatalities, i.e., on roads, railways, and bridges, originate from either accidents or suicides, natural death excluded. Knowing the correct manner of death is needed to work with optimal prevention strategies. The aims are to separate fatalities due to suicides, follow the development, and implement measures for suicide prevention. Methods are developed for suicide classification and criteria for the selection in which suicides were suspected. Fatalities in level one and two of five were classified as suicides. Data from the STA’s databases are used and so are data from the psychosocial investigations done by a trained investigator in the topic and with clinical experience from counselling at hospitals. 2129 persons died on the roads in Sweden, 10% (206 persons) were classified as suicides. 336 persons died after being hit by trains, 85% (284 persons) were suicides. 130 persons died by jumping from bridges.The number of suicides increases with population density. Suicide in the transport system is a major problem; firstly personal tragedies, it is also a work environment problem for truck and train drivers and for the emergency staff. It generates delays and costs for passenger and cargo transport. By analyzing the results of countermeasures in the form of obstructive barriers, the physical environment can be improved and high-risk areas can be accentuated. Restricting access to the means of suicide is important in suicide prevention. Strategies for the STA include suicide prevention in the design of new roads, railways, and bridges, as well as by identifying and reducing existing high-risk locations. Sharing the results with other authorities and organizations and cooperation within suicide prevention missions are vital for the enhancement of the overall suicide prevention work in society.
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Andersson, Anna-Lena, i Kenneth Svensson. "Suicide in the Transport System". W The Vision Zero Handbook, 1–13. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-23176-7_42-1.
Pełny tekst źródłaStreszczenie:
AbstractThe Swedish Transport Administration (STA) work to reduce the number of suicides in the transport system. Fatalities, i.e., on roads, railways, and bridges, originate from either accidents or suicides, natural death excluded. Knowing the correct manner of death is needed to work with optimal prevention strategies. The aims are to separate fatalities due to suicides, follow the development, and implement measures for suicide prevention. Methods are developed for suicide classification and criteria for the selection in which suicides were suspected. Fatalities in level one and two of five were classified as suicides. Data from the STA’s databases are used and so are data from the psychosocial investigations done by a trained investigator in the topic and with clinical experience from counselling at hospitals. 2129 persons died on the roads in Sweden, 10% (206 persons) were classified as suicides. 336 persons died after being hit by trains, 85% (284 persons) were suicides. 130 persons died by jumping from bridges.The number of suicides increases with population density. Suicide in the transport system is a major problem; firstly personal tragedies, it is also a work environment problem for truck and train drivers and for the emergency staff. It generates delays and costs for passenger and cargo transport. By analyzing the results of countermeasures in the form of obstructive barriers, the physical environment can be improved and high-risk areas can be accentuated. Restricting access to the means of suicide is important in suicide prevention. Strategies for the STA include suicide prevention in the design of new roads, railways, and bridges, as well as by identifying and reducing existing high-risk locations. Sharing the results with other authorities and organizations and cooperation within suicide prevention missions are vital for the enhancement of the overall suicide prevention work in society.
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"Defeating the High Weissenberg Number Problem". W Computational Rheology, 173–99. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2002. http://dx.doi.org/10.1142/9781860949425_0007.
Pełny tekst źródłaStreszczenia konferencji na temat "High Weissenberg number problem"
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Ashrafi, N., M. Mohamadali i M. Najafi. "High Weissenberg Number Stress Boundary Layer for the Upper Convected Maxwell Fluid". W ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-36544.
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The classic Blassius problem of steady boundary-layer flow of the upper convected Maxwell over a flat plate in a moving fluid is studied. According to scaling parameters the equations represent the viscoelastic stress boundary layer. By means of an exact similarity transformation, the non-linear viscoelastic momentum and constitutive equations transform into a system of highly nonlinear coupled ordinary differential equations. Numerical solution may be achieved by a variable stepping method for the initial-value problem. The stepping numerical method chosen fifth order Runge-Kutta for solving the resulting nonlinear algebraic equations at each step. It is seen that there is a stress boundary layer and there is no velocity boundary layer.
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Xue, Guanyang, Justin Caspar, Jaber Asiri, Xuanhong Cheng i Alparslan Oztekin. "Parametric Study of Viscoelastic Flow Simulations in Microfluidic Devices". W ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-95153.
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Abstract The open-source C++ toolbox OpenFOAM is used to perform the Computational Fluid Dynamics (CFD) simulations in two-dimensional microfluidic devices to characterize the viscoelastic flow. The Oldroyd-B constitutive equation is coupled with continuity and momentum equations. Multiple stabilization methods are applied to the numerical simulation to simulate High Weissenberg Number Problem (HWNP) in the microchannel. We applied the Log Conformation Reformulation (LCR) method to guarantee the positive definiteness of the stress tensor. The CUBISTA scheme and the improved Both Side Diffusion (iBSD) method are applied to predict the flow behavior at high elasticity regions without numerical oscillations. Various microstructures, including circles and flat plates, are placed in the center of the channel as the confinement. Our previous work demonstrated that the polyhedral mesh with hexahedral inflation layers effectively meshes complex microstructures in microchannels. A viscoelastic fluid is injected from the inlet at varying flow rates, corresponding to the local Weissenberg number up to 25. A parametric study is conducted on the first normal stress difference (N1) in specific regions with an accurate prediction of the viscoelastic flow field near the microstructures.
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Hagani, Fouad, M'hamed Boutaous, Ronnie Knikker, Shihe Xin i Dennis Siginer. "Numerical Modeling of Non-Affine Viscoelastic Fluid Flow Including Viscous Dissipation Through a Square Cross-Section Duct: Heat Transfer Enhancement due to the Inertia and the Elastic Effects". W ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23558.
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Abstract Non-isothermal laminar flow of a viscoelastic fluid including viscous dissipation through a square cross–section duct is analyzed. Viscoelastic stresses are described by Giesekus modele orthe Phan-Thien–Tanner model and the solvent shear stress is given by the linear Newtonian constitutive relationship. The flow through the tube is governed by the conservation equations of energy, mass, momentum associated with to one non–affine rheological model mentioned above. The mixed type of the governing system of equations (elliptic–parabolic–hyperbolic) requires coupling between discretisation methods designed for elliptic–type equations and techniques adapted to transport equations. To allow appropriate spatial discretisation of the convection terms, the system is rewritten in a quasi-linear first-order and homogeneous form without the continuity and energy equations. With the rheological models of the Giesekus type, the conformation tensor is by definition symmetrical and positive-definite, with the PTT model the hyperbolicity condition is subject to restrictions related to the rheological parameters. Based on this hyperbolicity condition, the contribution of the hyperbolic part is approximated by applying the characteristic method to extract pure advection terms which are then discretized by high ordre schemes WENO and HOUC. The algorithm thus developed makes it possible, to avoid the problems of instabilities related to the high Weissenberg number without the use of any stabilization method. Finally, a Nusselt number analysis is given as a function of inertia, elasticity, viscous dissipation, for constant solvent viscosity ratio and constant material and rheological parameters.
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Renardy, Michael. "Corner Singularities and High Weissenberg Number Asymptotics for Viscoelastic Fluids". W ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0230.
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Abstract Recent work on corner singularities in viscoelastic flows has shown that, in contrast to the Newtonian case, sharp boundary layers occur near the wall. These boundary layers can be viewed as a special instance of a more general phenomenon, which also occurs in other high Weissenberg number flows. This lecture reviews the derivation of boundary layer equations and their application, in particular to corner flow.
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Junio da Silva Furlan, Laison, Matheus Tozo de Araujo, Leandro Franco de Souza, Analice Costacurta Brandi i Marcio Teixeira de Mendonca. "Stability Analysis of Viscoelastic Fluid Flows for the High Weissenberg Number". W 25th International Congress of Mechanical Engineering. ABCM, 2019. http://dx.doi.org/10.26678/abcm.cobem2019.cob2019-2036.
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Carreira, Beatriz Liara, Analice Costacurta Brandi, Laison Junio da Silva Furlan, Matheus Tozo de Araujo i Leandro Franco de Souza. "Log-Conformation and Square Root-Conformation Transformations in High Weissenberg Number Flows". W 25th International Congress of Mechanical Engineering. ABCM, 2019. http://dx.doi.org/10.26678/abcm.cobem2019.cob2019-1949.
Pełny tekst źródła
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Carreira, Beatriz Liara, Analice Costacurta Brandi, Matheus Tozo de Araujo, Laison Junio da Silva Furlan i Leandro Franco de Souza. "HYDRODYNAMIC STABILITY ANALYSIS IN HIGH WEISSENBERG NUMBER FLOWS VIA LOG-CONFORMATION TRANSFORMATION". W 12th Spring School on Transition and Turbulence. ABCM, 2020. http://dx.doi.org/10.26678/abcm.eptt2020.ept20-0047.
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Jafari, Azadeh, Michel O. Deville i Nicolas Fiétier. "Spectral Elements Analysis for Viscoelastic Fluids at High Weissenberg Number Using Logarithmic conformation Tensor Model". W NUMERICAL ANALYSIS AND APPLIED MATHEMATICS: International Conference on Numerical Analysis and Applied Mathematics 2008. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2990912.
Pełny tekst źródła
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Amoura, Meriem, i Noureddine Zeraibi. "Effect of Viscous Dissipation on Heat Transfer Between Two Concentric Cylinders for Carreau Fluids". W ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24544.
Pełny tekst źródłaStreszczenie:
In this paper, we present a numerical study of the flow characteristics and heat transfer mechanism of a non-Newtonian fluid in an annular space between two coaxial rotating cylinders taking into account the effect of viscous dissipation. The Carreau stress-strain relation was adopted to model the rheological fluid behavior. The problem is studied when the heated inner cylinder rotates around the common axis with constant angular velocity and the cooled outer cylinder is at the rest. The horizontal endplates are assumed adiabatic. In-house code which is based on a Galerkin mixed finite element is developed to obtain numerical solutions of the complete governing equations and associated boundary conditions and is validated with the results reported in the literature. It is found that five parameters can describe the problem under consideration, the Reynolds number (Re), the Grashof number (Gr), the index of structure (n), Weissenberg number (We) and the Eckert number (Ec). The velocity, temperature and stream function distributions and the local Nusselt number variations are drawn for different dimensionless groups.
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Ashrafi, Nariman, i Sepideh Samghani. "Oscillating Viscoelastic Flow". W ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-85635.
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The flow of nonlinear viscoelastic fluids between oscillating parallel plates is investigated. The investigation features time-dependent analysis of a complicated viscoelastic material modeled based on the Johnson-Segalman constitutive relation. Given the rheological parameters of certain material known from experiments, the coefficients of Johnson-Segalman constitutive equation model for the material are evaluated by fitting the data. The problem is first formulated by writing the governing equations for the flow between two independently oscillating parallel plates, i.e. oscillating Couette flow. The velocity and stress are represented by symmetric and antisymmetric Chandrasekhar functions in space. Both inertia and normal stress effects are included. A numerical scheme is applied to solve the governing equations in time domain projected by Galerkin method. For given Reynolds number and viscosity ratio, one critical Weissenberg numbers is found at which an exchange of stability occurs between the Couette and other steady flows. The model is capable of predicting the nonlinear amplitude-dependent behavior of viscoelastic flows under single and multiple-frequency excitations.
Raporty organizacyjne na temat "High Weissenberg number problem"
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Oyekan, Khalimath, Ayodotun Ayorinde i Oreoluwa Adenuga. The Problem of Out-of-School Children in Nigeria. Research on Improving Systems of Education (RISE), marzec 2023. http://dx.doi.org/10.35489/bsg-rise-ri_2023/058.
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In 2015, all United Nations Member States adopted the 2030 Agenda for Sustainable Development which outlines a blueprint to address global challenges across a broad range of themes including poverty, health, education, inequality, climate change, environmental degradation, peace and justice. The Goal 4 of the 2030 Agenda for Sustainable Development, otherwise referred to as the United Nations Sustainable Development Goal 4, seeks to ensure inclusive and equitable quality education and promote lifelong learning opportunities for all. Unfortunately, an approximated 263 million children remain out of school around the world. This number includes children who never started formal schooling and children who started school but later dropped out (United Nations Educational, Scientific and Cultural Organization [UNESCO], 2016). Reducing the number of out-of-school children (OOSC) is a key priority for countries across Sub-Saharan Africa, including Nigeria. This is because more than half of children globally that have not enrolled in school live in Sub-Saharan Africa, and more than 85 percent of children in Sub-Saharan Africa are not learning the minimum (UNESCO Institute of Statistics, 2018). Moreover, education is a fundamental human right, a critical driver for economic advancement and a powerful tool for poverty reduction. Hence, no child of school age should be denied access to quality and equitable education, and an opportunity to acquire skills that guarantee future employability and long-term earning. In the Nigerian context, OOSC are prevalent in both rural and urban settings, but rural areas, and isolated or deprived areas in general, consistently show higher numbers of out-of-school children (World Bank, 2019). These children are spread across the country in varying proportions. This situation is of concern to the Federal Government of Nigeria as noted in the Nigeria Education Ministerial Plan (2018-2022) which outlines several strategies targeted at bringing children back to school. In spite of these strategies, the number of OOSC remains significantly high. This insight note aims to provide an overview of the most recent data on out-of-school children in Nigeria, including breakdowns by socioeconomic and other demographic indicators. This will be followed by suggestions of possible interventions, prime of which is the Accelerated Education Programme (AEP), and other interventions which could serve to strengthen the existing laid out strategies by the government in addressing the OOSC problem in Nigeria.
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TERENTIEV, S., O. GRUNINA i L. PONOMAREVA. FEATURES OF THE PRODUCTION OF DOUGH SEMI-FINISHED PRODUCT PRODUCED USING LENTIL FLOUR. Science and Innovation Center Publishing House, 2022. http://dx.doi.org/10.12731/2070-7568-2022-11-2-4-15-22.
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Bread consumption has a stable increase in the territory of Russia and in particular in the Ulyanovsk and Samara regions. Bread, as a fairly low-priced product, is in high demand among consumers, but this product is not biologically saturated with useful substances, therefore, in modern production, a number of techniques are used to increase the nutritional and biological value of these types of products. In our work, one of these methods will be considered - the introduction of lentil flour into dough preparations. The problem is that the state policy regarding import substitution, aimed at replacing food additives produced abroad, necessitates the use of food additives or raw materials of natural origin produced in the territory of the Russian Federation, and the lack of development of regulatory and technological documentation in this direction is a significant problem for public enterprises. nutrition. Purpose - to carry out the development of a recipe for a test semi-finished product produced with the addition of lentil flour, as a product with a preventive purpose Results: based on the results of the study, a recipe for a test semi-finished product was developed, produced with the addition of lentil flour, as a product with a preventive purpose.
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Ayoul-Guilmard, Q., S. Ganesh, M. Nuñez, R. Tosi, F. Nobile, R. Rossi i C. Soriano. D5.4 Report on MLMC for time dependent problems. Scipedia, 2021. http://dx.doi.org/10.23967/exaqute.2021.2.005.
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In this report, we study the use of Multi-Level Monte Carlo (MLMC) methods for time dependent problems. It was found that the usability of MLMC methods depends strongly on whether or not the underlying time dependent problem is chaotic in nature. Numerical experiments are conducted on both simple problems, as well as fluid flow problems of practical interest to the ExaQUte project, to demonstrate this. For the non-chaotic cases, the hypotheses that enable the use of MLMC methods were found to be satisfied. For the chaotic cases, especially the case of high Reynolds’ number fluid flow, the hypotheses were not satisfied. However, it was found that correlations between the different levels were high enough to merit the use of multi-fidelity or control-variate approaches. It was also noted that MLMC methods could work for chaotic problems if the time window of analysis were chosen to be small enough. Future studies are proposed to examine this possibility.
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Symonenko, Svitlana V., Nataliia V. Zaitseva, Viacheslav V. Osadchyi, Kateryna P. Osadcha i Ekaterina O. Shmeltser. Virtual reality in foreign language training at higher educational institutions. [б. в.], luty 2020. http://dx.doi.org/10.31812/123456789/3759.
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The paper deals with the urgent problem of application of virtual reality in foreign language training. Statistical data confirms that the number of smartphone users, Internet users, including wireless Internet users, has been increasing for recent years in Ukraine and tends to grow. The coherence of quick mobile Internet access and presence of supplementary equipment enables to get trained or to self-dependently advance due to usage of virtual reality possibilities for education in the stationary classrooms, at home and in motion. Several important features of virtual reality, its advantages for education are discussed. It is noted that virtual reality is remaining a relatively new technology in language learning. Benefits from virtual reality implementation into foreign language learning and teaching are given. The aspects of immersion and gamification in foreign language learning are considered. It is emphasized that virtual reality creates necessary preconditions for motivation increasing. The results of the survey at two higher education institution as to personal experience in using VR applications for learning foreign languages are presented. Most students at both universities have indicated quite a low virtual reality application usage. Six popular virtual reality applications for foreign language learning (Mondly, VRSpeech, VR Learn English, Gold Lotus, AltSpaceVR and VirtualSpeech) are analyzed. It is stated that the most preferred VR application for foreign language learning includes detailed virtual environment for maximal immersion, high- level visual effects similar to video games, simple avatar control, thorough material selection and complete complicity level accordance of every element and aspect, affordability, helpful and unobtrusive following up.
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Malej, Matt, i Fengyan Shi. Suppressing the pressure-source instability in modeling deep-draft vessels with low under-keel clearance in FUNWAVE-TVD. Engineer Research and Development Center (U.S.), maj 2021. http://dx.doi.org/10.21079/11681/40639.
Pełny tekst źródłaStreszczenie:
This Coastal and Hydraulics Engineering Technical Note (CHETN) documents the development through verification and validation of three instability-suppressing mechanisms in FUNWAVE-TVD, a Boussinesq-type numerical wave model, when modeling deep-draft vessels with a low under-keel clearance (UKC). Many large commercial ports and channels (e.g., Houston Ship Channel, Galveston, US Army Corps of Engineers [USACE]) are traveled and affected by tens of thousands of commercial vessel passages per year. In a series of recent projects undertaken for the Galveston District (USACE), it was discovered that when deep-draft vessels are modeled using pressure-source mechanisms, they can suffer from model instabilities when low UKC is employed (e.g., vessel draft of 12 m¹ in a channel of 15 m or less of depth), rendering a simulation unstable and obsolete. As an increasingly large number of deep-draft vessels are put into service, this problem is becoming more severe. This presents an operational challenge when modeling large container-type vessels in busy shipping channels, as these often will come as close as 1 m to the bottom of the channel, or even touch the bottom. This behavior would subsequently exhibit a numerical discontinuity in a given model and could severely limit the sample size of modeled vessels. This CHETN outlines a robust approach to suppressing such instability without compromising the integrity of the far-field vessel wave/wake solution. The three methods developed in this study aim to suppress high-frequency spikes generated nearfield of a vessel. They are a shock-capturing method, a friction method, and a viscosity method, respectively. The tests show that the combined shock-capturing and friction method is the most effective method to suppress the local high-frequency noises, while not affecting the far-field solution. A strong test, in which the target draft is larger than the channel depth, shows that there are no high-frequency noises generated in the case of ship squat as long as the shock-capturing method is used.
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Perkins, Dustin. Invasive exotic plant monitoring at Dinosaur National Monument: Results of the 2019 field season on the Green River, and the third completed monitoring rotation. Redaktor Alice Wondrak Biel. National Park Service, grudzień 2021. http://dx.doi.org/10.36967/nrr-2284627.
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Invasive exotic plant (IEP) species are a significant threat to natural ecosystem integrity and biodiversity, and controlling them is a high priority for the National Park Service. The Northern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. We also calculated a patch management index (PMI) to quantify the extent and density of invasive patches into a single value that helps identify the scale of the problem. Park managers can use this tool to help prioritize IEP treatment. At Dinosaur National Monument, the NCPN monitors IEPs in the Green and Yampa river corridors. This report summarizes data from monitoring on the Green River in 2019, and monitoring on the Yampa River in 2017, to represent the completion of the third monitoring rotation of the entire river corridor (2002–2005, 2010–2011, 2017–2019). During surveys conducted from June 26 to July 2, 2019, NCPN staff detected 12 priority IEP species and two non-priority species in a 84.6-hectare (209-acre) area along 74.4 kilometers of the Green River above (“upper”) and below (“low-er”) its confluence with the Yampa. A total of 2,535 IEP patches were detected. Of those patches, 24.2% and 15.6% were smaller than 40 m2 on the upper and lower Green River reaches, respectively. The patch management index (PMI) was low or very low for 95.7% of patches on the upper Green River and 90.9% of patches on the lower Green River. Tamarisk (Tamarix sp.), broad-leaf pepperwort (Lepidium latifolium), and yellow sweetclover (Meli-lotus officinalis) were the most widespread species. For the first time, NCPN monitoring detected teasel (Dipsacus sylvestris) on the upper Green River. Yellow sweetclover has increased on all three river reaches during the survey years. Musk thistle (Carduus nutans) was found at considerably lower levels than yellow sweetclover but has also increased on all three river reaches. Leafy spurge is increasing on the lower Green River and Yampa River. Cheatgrass was not monitored in the first rotation, but increased substantially in cover and percent frequency on all three river sections from 2010–2011 to 2017–2019. This increase may be due to a lack of recent high-flow scouring events. The highly regulated upper Green River generally has the highest number of IEPs, while the lower Green River has a moderate amount of IEPs. The largely unregulated flows of the Yampa River continue to result in a lower number of patches per kilometer, lower percent cover, and lower percent frequency than the upper or lower Green River. Network staff will return to the monument in 2022 to begin the fourth monitoring rotation.
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Duvvuri, Sarvani, i Srinivas S. Pulugurtha. Researching Relationships between Truck Travel Time Performance Measures and On-Network and Off-Network Characteristics. Mineta Transportation Institute, lipiec 2021. http://dx.doi.org/10.31979/mti.2021.1946.
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Trucks serve significant amount of freight tonnage and are more susceptible to complex interactions with other vehicles in a traffic stream. While traffic congestion continues to be a significant ‘highway’ problem, delays in truck travel result in loss of revenue to the trucking companies. There is a significant research on the traffic congestion mitigation, but a very few studies focused on data exclusive to trucks. This research is aimed at a regional-level analysis of truck travel time data to identify roads for improving mobility and reducing congestion for truck traffic. The objectives of the research are to compute and evaluate the truck travel time performance measures (by time of the day and day of the week) and use selected truck travel time performance measures to examine their correlation with on-network and off-network characteristics. Truck travel time data for the year 2019 were obtained and processed at the link level for Mecklenburg County, Wake County, and Buncombe County, NC. Various truck travel time performance measures were computed by time of the day and day of the week. Pearson correlation coefficient analysis was performed to select the average travel time (ATT), planning time index (PTI), travel time index (TTI), and buffer time index (BTI) for further analysis. On-network characteristics such as the speed limit, reference speed, annual average daily traffic (AADT), and the number of through lanes were extracted for each link. Similarly, off-network characteristics such as land use and demographic data in the near vicinity of each selected link were captured using 0.25 miles and 0.50 miles as buffer widths. The relationships between the selected truck travel time performance measures and on-network and off-network characteristics were then analyzed using Pearson correlation coefficient analysis. The results indicate that urban areas, high-volume roads, and principal arterial roads are positively correlated with the truck travel time performance measures. Further, the presence of agricultural, light commercial, heavy commercial, light industrial, single-family residential, multi-family residential, office, transportation, and medical land uses increase the truck travel time performance measures (decrease the operational performance). The methodological approach and findings can be used in identifying potential areas to serve as truck priority zones and for planning decentralized delivery locations.
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NELYUBINA, E., i L. PANFILOVA. ASSESSMENT OF THE QUALITY OF EDUCATIONAL ELECTRONIC PUBLICATIONS AND RESOURCES. Science and Innovation Center Publishing House, 2021. http://dx.doi.org/10.12731/2658-4034-2021-12-4-2-85-97.
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Now the whole life of a person has switched to online mode. These changes also affected the education system. This means the need to introduce new technologies into the educational process. Books, manuals, printed publications are being replaced by electronic educational resources. Providing up-to-date, verified information to students has always been and remains one of the most important functions of the teacher. Unfortunately, with the transition of training to the online mode, the teacher cannot use his literature when conducting classes. In this regard, there is a need to use electronic resources. On the one hand, the development of the global network implies the presence of a large number of a wide variety of sites, which cannot but be a positive aspect, because both the teacher and the student can independently choose a resource that will be most understandable. But on the other hand, the variety of Internet resources implies the presence of unverified, false information, which can negatively affect the quality of education. That is why it is necessary to analyze new information systems. The problem is the presence of a large number of information technologies and resources used in education. Purpose. The goal is to conduct a comparative analysis of educational electronic publications and resources most often used by teachers of the natural science cycle in terms of their fullness, accessibility and use in the educational process. Method or methodology of the work. The requirements for the organization of a comprehensive examination suggest an approach that includes an examination of technical and technological, psychological, pedagogical and design-ergonomic aspects of the creation and use of educational electronic publications and resources, in our work we were based precisely on generalized research methods: 1) Technical and technological expertise (technical component of the site, its position in the network). 2) Psychological and pedagogical expertise (component by the type of educational electronic publication or resource, level of education, type and form of the educational process, assessment of the content and scenario of the informatization tool). 3) Design-ergonomic expertise (assessment of the quality of interface components of educational electronic publications and resources, their compliance with uniform ergonomic, aesthetic and health-saving requirements; assessment of the quality of interface components of educational electronic editions and resources, their compliance with uniform ergonomic, aesthetic and health-saving requirements). Results. The main sites that are frequently used by teachers of the natural science cycle of disciplines are the Russian Textbook corporation, the Enlightenment group of companies, the Binom publishing house, the Digital Age School, the practical significance of the study is determined by the high level of readiness of the results obtained, during the study it was found that it is advisable to introduce an information-electronic educational site - the Russian textbook corporation - into the pedagogical practice of the implementation of natural science subjects. The advantages of this server were established and recommendations for its use in the educational process were developed. Practical implications: the results obtained are expedient to be applied in educational institutions of the Russian Federation.
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Samochowiec, Jakub, Johannes C. Bauer i Kathrin Neumüller. Strategies for Dealing With the Labour Shortage – An Overview. Gdi-verlag, GDI Gottlieb Duttweiler Institute, czerwiec 2023. http://dx.doi.org/10.59986/hcmm6371.
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The Swiss labour market will shrink without immigration. But even with high immigrationnfigures, it will not be possible to maintain the previous growth of the labour market. Employers need to adapt to this situation. This study compiles and arranges different measures for dealing with the labour shortage, with the aim of showing different approaches to deal with the situation. The measures are arranged following the formula: Number of person-hours x efficiency = output The increase in the number of person-hours includes, on the one hand, measures to make employers more attractive. These are relative competitive advantages in the labour market. In a survey, 1,000 employees from German-speaking Switzerland were asked about their satisfaction with different aspects of their work and these areas of satisfaction were compared with their overall satisfaction, loyalty toward their employer and intentions of quitting their jobs. It showed that development opportunities (both personal and in terms of their career) and the appreciation by an employer who matches one’s values are the most important employer attributes for employees, but it is precisely the development opportunities that are often not offered to a satisfactory extent. The increase in the number of person-hours comprises, on the other hand, measures to expand labour market participation, which means that more person-hours are worked in the market. There are many options for this. Where remote working has become the norm, there are not many obstacles to offshoring work abroad. In addition, pensioners are open to working on a project-by-project basis and, if need be, could be recruited via “gig-economy” style platforms for individual tasks. A corporate platform could lower the hurdle for pensioners who worked for that company (in terms of psychology and also the bureaucracy) and create a broad but casual recruitment pool. Furthermore, career and pension advice could encourage women to increase their working hours or at least to not to give up their jobs completely despite high childcare costs. Political measures could also be introduced to lower the latter. It is probable that the labour market of the future will have to cope with fewer people, despite all efforts to increase person-hours. The formula suggests another factor: the increase in efficiency. Automation of work processes is one example of an efficiency measure. In a survey of managers, half of the respondents thought that about 20% of the work could already be automated today. However, there was a lack of competencies (also a consequence of the labour shortage), of a technology-savvy culture and of confidence that quality can be maintained. In addition, respondents to the employee survey also perceive about 20% of the work they do as unnecessary (excessive emails, meetings, administrative tasks, etc.). This is partly attributed to too much in-house bureaucracy and too many managers – which is the occupational group that has grown the most in the swiss labor market since 1991. The connection between wages and value generation seems to be restricted both within companies and in society as a whole. The labour shortage is often also caused by an allocation problem. Even measures to increase efficiency do not necessarily lead to less need for staff. Rather, the consequence of increased efficiency is often an almost automatic expansion GDI Gottlieb Duttweiler Institute 5 of output. In order to cope with the labour shortage, it is necessary to deal with output carefully and to reflect on where output should be expanded, capped or even reduced so that any reduction in output is done in a controlled manner. Especially in the context of an increasing relevance of sustainability, there are services and products in all companies that need to be questioned and the elimination of which would promote the credibility of sustainability strategies and thus also increase the chance that the corporate values match those of young employees. Perhaps other legal forms are necessary in order to avoid the pressures for growth which are linked with a shareholder structure. Alternative models are possible.
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Landau, Sergei Yan, John W. Walker, Avi Perevolotsky, Eugene D. Ungar, Butch Taylor i Daniel Waldron. Goats for maximal efficacy of brush control. United States Department of Agriculture, marzec 2008. http://dx.doi.org/10.32747/2008.7587731.bard.
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Background. Brush encroachment constitutes a serious problem in both Texas and Israel. We addressed the issue of efficacy of livestock herbivory - in the form of goat browsing - to change the ecological balance to the detriment of the shrub vegetation. Shrub consumption by goats is kept low by plant chemical defenses such as tannins and terpenes. Scientists at TAES and ARO have developed an innovative, cost-effective methodology using fecal Near Infrared Spectrometry to elucidate the dietary percentage of targeted, browse species (terpene-richredberry and blueberry juniper in the US, and tannin-rich Pistacialentiscus in Israel) for a large number of animals. The original research objectives of this project were: 1. to clarify the relative preference of goat breeds and the individual variation of goats within breeds, when consuming targeted brush species; 2. to assess the heritability of browse intake and validate the concept of breeding goat lines that exhibit high preference for chemically defended brush, using juniper as a model; 3. to clarify the relative contributions of genetics and learning on the preference for target species; 4. to identify mechanisms that are associated with greater intake of brush from the two target species; 5. to establish when the target species are the most vulnerable to grazing. (Issue no.5 was addressed only partly.) Major conclusions, solutions, achievements: Both the Israel and US scientists put significant efforts into improving and validating the technique of Fecal NIRS for predicting the botanical composition of goat diets. Israeli scientists validated the use of observational data for calibrating fecal NIRS, while US scientists established that calibrations could be used across animals differing in breed and age but that caution should be used in making comparisons between different sexes. These findings are important because the ability to select goat breeds or individuals within a breed for maximal efficiency of brush control is dependent upon accurate measurement of the botanical composition of the diet. In Israel it was found that Damascus goats consume diets more than twice richer in P. lentiscus than Mamber or Boer goats. In the US no differences were found between Angora and Boer cross goats but significant differences were found between individuals within breeds in juniper dietary percentage. In both countries, intervention strategies were found that further increased the consumption of the chemically defended plant. In Israel feeding polyethylene glycol (PEG, MW 4,000) that forms high-affinity complexes with tannins increased P. lentiscus dietary percentage an average of 7 percentage units. In the US feeding a protein supplement, which enhances rates of P450-catalyzed oxidations and therefore the rate of oxidation of monoterpenes, increased juniper consumption 5 percentage units. However, the effects of these interventions were not as large as breed or individual animal effects. Also, in a wide array of competitive tannin-binding assays in Israel with trypsin, salivary proteins did not bind more tannic acid or quebracho tannin than non-specific bovine serum albumin, parotid saliva did not bind more tannins than mixed saliva, no response of tannin-binding was found to levels of dietary tannins, and the breed effect was of minor importance, if any. These fundings strongly suggest that salivary proteins are not the first line of defense from tannin astringency in goats. In the US relatively low values for heritability and repeatability for juniper consumption were found (13% and 30%, respectively), possibly resulting from sampling error or non-genetic transfer of foraging behavior, i.e., social learning. Both alternatives seem to be true as significant variation between sequential observations were noted on the same animal and cross fostering studies conducted in Israel demonstrated that kids raised by Mamber goats showed lower propensity to consume P. lentiscus than counterparts raised by Damascus goats.