mean current
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2021 ◽  
Vol 26 (4) ◽  
pp. 619-634
Author(s):  
Paul Guyer

AbstractCan Kant’s theory of fine art serve as a theory of modern art? It all depends on what ‘modern’ means. The word can mean current or contemporary, indexed to the time of use, and in that sense the answer is yes: Kant’s theory of genius implies that successful art is always to some extent novel, so there should always be something that counts as contemporary art on his theory. But ‘modern’ can also be used adjectively, perhaps more properly as ‘modernist’, to refer to art of a particular moment, in some cases superseded by postmodern art. Kant’s theory is not a theory of modernist art in at least one prominent form, the formalism of Clement Greenberg. But other theories, such as those of George Dickie and Arthur Danto, although triggered by particular works of modernist art and meant to accommodate them, were meant to be theories of what art was always doing, and Kant’s is too. In that sense it can be considered a modern theory of art but not a theory of modern art.


2021 ◽  
Vol 9 (9) ◽  
pp. 986
Author(s):  
Chunye Hu ◽  
Jialing Hao ◽  
Zhen Liu

Classical eddy viscosity model deviates from the actual mean current profiles, when calculating the mean current profiles over rippled-beds in the presence of non-breaking waves, owing to the neglect of the enhancement of the wave boundary layer thickness by ripples and the wave-induced shear stress (the radiation stress and the wave Reynolds stress). Considering these shortcomings, a semi-empirical one-dimensional vertical (1DV) model is presented in this study. The present model was obtained using the two-dimensional Navier–Stokes equations and eddy viscosity assumptions, which differ from those of previous researchers, while a top-to-bottom sequence was adopted to calculate the mean current profiles. Empirical formulae were derived from the laboratory measurements and used in the present model to accurately predict the wave boundary layer thickness and bed roughness. The present model is in satisfactory agreement with the data from laboratory experiments. The factors influencing the mean current profiles were analyzed also. The wave-induced second-order shear stresses were found to be the principal reason for the deviations of the mean current profiles in the near-surface layer; as the influencing factors of wave-induced shear stress, the intensity of the wave relative to the current, the angle between the wave and current, and the size of ripples can also have a non-negligible effect on the mean current profiles.


2021 ◽  
Vol 37 (4) ◽  
Author(s):  
A. A. Slepyshev ◽  

Purpose. The paper is aimed at investigating the momentum vertical transfer by inertia-gravity internal waves on a two-dimensional flow with a vertical shear of velocity, and also at studying the Stokes drift of liquid particles and the mean current effect on it. Methods and Results. Free internal waves in an infinite basin of constant depth are considered in the Boussinesq approximation with the regard for the Earth rotation. Two components of the mean current velocity depend on the vertical coordinate. The equation for the vertical velocity amplitude has complex coefficients; therefore the eigenfunction and the wave frequency are complex. The corresponding boundary value problem is solved numerically by the implicit Adams scheme of the third order of accuracy. The wave frequency at a fixed wavenumber was found by the shooting method. It was determined that the frequency imaginary part was small and could be either negative or positive depending on a wave number and a mode number. Thus, both weak attenuation and weak amplification of an internal wave are possible. The vertical wave momentum fluxes are nonzero and can exceed the corresponding turbulent fluxes. The Stokes drift velocity, transverse to the wave direction, is nonzero and less than the longitudinal velocity. The vertical component of the Stokes drift velocity is also nonzero and four orders of magnitude less than the longitudinal component. The signs of the vertical component of the Stokes drift velocity for the waves with the frequencies 10 and 16 cycle/h are opposite, since the signs of their frequency imaginary parts are different; and the vertical component of the Stokes drift velocity is proportional to the wave frequency imaginary part. Conclusions. The vertical momentum wave flux of inertia-gravity internal waves differs from zero in the presence of the current whose velocity component, transverse to the wave propagation direction, depends on the vertical coordinate. The component of the Stokes drift velocity, transverse to the wave propagation direction, is nonzero and less than the longitudinal one. The vertical component of the Stokes drift velocity is also nonzero and can contribute to formation of the vertical fine structure


2021 ◽  
Vol 28 (4) ◽  
Author(s):  
A. A. Slepyshev ◽  

Purpose. The paper is aimed at investigating the momentum vertical transfer by inertia-gravity internal waves on a two-dimensional flow with a vertical shear of velocity, and also at studying the Stokes drift of liquid particles and the mean current effect on it. Methods and Results. Free internal waves in an infinite basin of constant depth are considered in the Boussinesq approximation with the regard for the Earth rotation. Two components of the mean current velocity depend on the vertical coordinate. The equation for the vertical velocity amplitude has complex coefficients; therefore the eigenfunction and the wave frequency are complex. The corresponding boundary value problem is solved numerically by the implicit Adams scheme of the third order of accuracy. The wave frequency at a fixed wavenumber was found by the shooting method. It was determined that the frequency imaginary part was small and could be either negative or positive depending on a wave number and a mode number. Thus, both weak attenuation and weak amplification of an internal wave are possible. The vertical wave momentum fluxes are nonzero and can exceed the corresponding turbulent fluxes. The Stokes drift velocity, transverse to the wave direction, is nonzero and less than the longitudinal velocity. The vertical component of the Stokes drift velocity is also nonzero and four orders of magnitude less than the longitudinal component. The signs of the vertical component of the Stokes drift velocity for the waves with the frequencies 10 and 16 cph are opposite, since the signs of their frequency imaginary parts are different; and the vertical component of the Stokes drift velocity is proportional to the wave frequency imaginary part. Conclusions. The vertical momentum wave flux of inertia-gravity internal waves differs from zero in the presence of the current whose velocity component, transverse to the wave propagation direction, depends on the vertical coordinate. The component of the Stokes drift velocity, transverse to the wave propagation direction, is nonzero and less than the longitudinal one. The vertical component of the Stokes drift velocity is also nonzero and can contribute to formation of the vertical fine structure.


2021 ◽  
Vol 9 (8) ◽  
pp. 791
Author(s):  
Duoc Tan Nguyen ◽  
Ad J. H. M. Reniers ◽  
Dano Roelvink

In numerical ocean models, the effect of waves on currents is usually expressed by either vortex-force or radiation stress representations. In this paper, the differences and similarities between those two representations are investigated in detail in conditions of both conservative and nonconservative waves. In addition, comparisons between different sets of equations of mean motion that apply different representations of wave-induced forcing terms are included. The comparisons are useful for selecting a suitable numerical ocean model to simulate the mean current in conditions of waves combined with currents.


2021 ◽  
Vol 9 (6) ◽  
pp. 664
Author(s):  
Hui Chen ◽  
Shaofeng Li ◽  
Jinbao Song ◽  
Hailun He

This study aimed to highlight a general lack of clarity regarding the scale of the temporal averaging implicit in Ekman-type models. Under the assumption of time and depth-dependent eddy viscosity, we present an analytical Fourier series solution for a wave-modified Ekman model. The depth dependence of eddy viscosity is based on the K-Profile Parameterization (KPP) scheme. The solution reproduces major characteristics of diurnal variation in ocean velocity and shear. Results show that the time variability in eddy viscosity leads to an enhanced mean current near-surface and a decrease in the effective eddy viscosity, which finally results in an intensified near-surface shear and wakes a low-level jet flow. Rectification values are dominated by the strength of diurnal mixing, and partly due to the nonlinear depth dependence of the eddy viscosity.


Author(s):  
W. D. Smyth ◽  
S. J. Warner ◽  
J. N. Moum ◽  
H. Pham ◽  
S. Sarkar

AbstractFactors thought to influence deep cycle turbulence in the equatorial Pacific are examined statistically for their predictive capacity using a 13-year moored record that includes microstructure measurements of the turbulent kinetic energy dissipation rate. Wind stress and mean current shear are found to be most predictive of the dissipation rate. Those variables, together with the solar buoyancy flux and the diurnal mixed layer thickness, are combined to make a pair of useful parameterizations. The uncertainty in these predictions is typically 50% greater than the uncertainty in present-day in situ measurements. To illustrate the use of these parameterizations, the record of deep cycle turbulence, measured directly since 2005, is extended back to 1990 based on historical mooring data. The extended record is used to refine our understanding of the seasonal variation of deep cycle turbulence.


Author(s):  
Sarah El Archi ◽  
◽  
Paul Brunault ◽  
Nicolas Ballon ◽  
Christian Réveillère ◽  
...  

"Background: Several psychological features are implicated in the dieting success. Better understanding of these features may allow reducing dieting failure of both surgical and non-surgical weight loss interventions, especially for individuals with food addiction (FA). In non-clinical population, low perceived self-regulatory success (PSRS) in dieting is associated with higher BMI (body mass index), FA, food craving and impulsivity. PSRS could partially explain weight gain in FA, but no study investigated this association in the specific FA population. Method: To diagnose FA, 288 women recruited online completed The Yale Food Addiction Scale 2.0. They also completed the following self-administrated questionnaires: the French adaptation of the PSRS in dieting scale, the Food Craving Questionnaire Trait-Reduced, and the Barratt Impulsivity Scale-11. They specified their height, current and lifetime maximal weight, and if they were in a current diet. Mean age was 26.1±10.3 years. Mean current BMI was 23.4±5.5 kg/m². Results: 79 women met criteria for FA (27.4%), indicating significant less PSRS in dieting and higher probability to be in a current diet to lose weight. In the whole population (n=288), PSRS in dieting was negatively correlated with current and lifetime maximal BMI, food craving, FA, attentional and non-planning impulsivity. In a multiple linear regression conducted in the subgroup of women with FA, PSRS score was predicted by age, current BMI, food addiction and food craving. More, results suggested food craving enable the association between food addiction and PSRS. Conclusion: These results showed the high preoccupation about food intake and weight gain in the FA population. Psychological features associated with FA such as food craving and impulsivity, seem to impact the PSRS in dieting, increasing psychological vulnerability."


Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 439
Author(s):  
Gheorghe-Marian Tudoran ◽  
Avram Cicșa ◽  
Albert Ciceu ◽  
Alexandru-Claudiu Dobre

This study presents the biometric relationships among various increments that is useful in both scientific and practical terms for the silvicultural of silver fir. The increments recorded in the biometric characteristics of trees are a faithful indicator of the effect of silvicultural work measures and of environmental conditions. Knowing these increments, and the relationships among them, can contribute to adaptations in silvicultural work on these stands with the purpose of reducing risks generated by environmental factors. We carried an inventory based on tree increment cores. The sample size was determined based on both radial increment and height increment variability of the trees. The sample trees were selected in proportion to their basal area on diameter categories. Current annual height increment (CAIh) was measured on felled trees from mean tree category. For CAIh we generated models based on the mean tree height. Percentages of the basal area increment and of form-height increment were used to compute the current annual volume increment percentage (PCAIv). For the mean tree, the CAIh estimated through the used models had a root-mean-square error (RMSE) of 0.8749 and for the current annual volume increment (CAIv) the RMSE value was 0.1295. In even-aged stands, the mean current volume increment tree is a hypothetical tree that may have the mean basal area of all the trees and the form-height of the stand. Conclusions: The diameter, height, and volume increments of trees are influenced by structural conditions and natural factors. The structures comprising several generations of fir mixed with beech and other deciduous trees, which have been obtained by the natural regeneration of local provenances, are stable and must become management targets. Stable structures are a condition for the sustainable management of stands.


Author(s):  
S. W. Stevens ◽  
R. Pawlowicz ◽  
S. E. Allen

AbstractThe intermediate circulation of the Strait of Georgia, British Columbia, Canada, plays a key role in dispersing contaminants throughout the Salish Sea, yet little is known about its dynamics. Here, we use hydrographic observations and hindcast fields from a regional 3D model to approach the intermediate circulation from three perspectives. Firstly, we derive and model a “seasonality” tracer from temperature observations to age the water, estimate mixing, and infer circulation. Secondly, we analyze modeled velocity fields to create mean current maps and examine the advective and diffusive components of the mean flow field. Lastly, we calculate Lagrangian trajectories to derive Transit Time Distributions and Lagrangian statistics. In combination, these analyses provide an overview of the mean intermediate circulation that can be summarized as follows: subducting water in Haro Strait ventilates the intermediate water primarily via an up-strait boundary current that flows along the eastern shores of the southernmost basin in 1–2 months. This inflowing water is either incorporated into the interior of the basin, recirculated southwards, or transported into the northernmost basin, mixing steadily with adjacent water masses during its transit. A second, shallower ventilating jet emanates southwards from Discovery Passage, locally modifying the Haro Strait inflow signal. Outside of these well-defined advective features, diffusive transport dominates in the majority of the region. The intermediate renewal signal fully ventilates the region in 100–140 days, which serves as a benchmark for contaminant dispersal timescale estimates.


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