scholarly journals Mode selection in trailing vortices: harmonic response of the non-parallel Batchelor vortex

2016 ◽  
Vol 790 ◽  
pp. 523-552 ◽  
Author(s):  
Francesco Viola ◽  
Cristobal Arratia ◽  
François Gallaire
Keyword(s):  
Linear Response ◽  
Energy Content ◽  
Mode Selection ◽  
Nonlinear Excitation ◽  
Harmonic Forcing ◽  
Parallel Flows ◽  
Trailing Vortices ◽  
Resolvent Approach ◽  
Globally Stable ◽  
Good Agreement

In the present study, the response of model trailing vortices subjected to a harmonic forcing is studied. To this purpose, a globally stable non-parallel Batchelor vortex is considered as the baseflow. Direct numerical simulations (DNS) show that a large variety of helical responses can be excited and amplified through the domain when a harmonic inlet forcing is imposed. The spatial shape of the responses strongly depends on the forcing frequency, with the appearance of modes with progressively higher azimuthal wavenumber $m$ as the frequency increases. The mode-selection mechanism is shown to be directly connected to the local stability properties of the flow, and is simultaneously investigated by a WKB (Wentzel, Kramers, Brillouin) approximation in the framework of weakly non-parallel flows and by the global resolvent approach. In addition to the excellent agreement between the two (local and global) approaches for the computation of the linear response to harmonic forcing at the inlet, the usual WKB analysis is extended to a suitably chosen type of harmonic body forcing, showing also good agreement with the corresponding global results. As expected, the gain of the nonlinear response is significantly lower than that of the linear response, but the mode selection observed in the DNS as a function of the forcing frequency can be predicted fairly accurately by the linear analysis. Finally, by comparing the linear and nonlinear results in terms of energy content for different $m$, we suggest that the origin of the meandering observed in trailing-vortex experiments could be due to a nonlinear excitation stemming consistently at $m=1$ from the competition between the leading linear modes.

First-Principles Study of Structural and Vibrational Properties of α-SiO2 under Pressure

2015 ◽  
Vol 775 ◽  
pp. 191-196
Author(s):  
Xiao Wei Lei ◽  
Yong Song ◽  
Kuo Yang ◽  
Hui Zhao
Keyword(s):  
High Pressure ◽  
Perturbation Theory ◽  
Infrared Spectra ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Vibrational Properties ◽  
Vibrational Modes ◽  
Density Functional Perturbation Theory ◽  
Good Agreement

Using first principles approach, we present the structural, vibrational and dielectric properties of α-SiO2. The calculations have been carried out within the density functional perturbation theory and linear response formalism using the norm-concerving pseudopotentials and a plane wave basis. All the vibrational modes identified are in good agreement with experiment. The calculated infrared spectra are also in good agreement with available experimental results both for the positions and the intensities of the main peaks. We find that the modes Eu7 and A2u4 splits in two respectively at high hydrostaticpressures. Then we calculate the infrared spectra under high pressure of different orientations. The vibrational modes in different phase transitions are reported and discussed respectively.

scholarly journals Intake of copper, iron, manganese and zinc by healthy, exclusively-breast-fed infants during the first 3 months of life

1979 ◽  
Vol 42 (3) ◽  
pp. 407-411 ◽  
Author(s):  
E. Vuori
Keyword(s):  
Trace Elements ◽  
Breast Milk ◽  
Trace Element ◽  
Energy Content ◽  
Human Nutrition ◽  
Expert Committee ◽  
Food And Nutrition ◽  
Iron Manganese ◽  
Breast Fed ◽  
Good Agreement

1. The calculated median daily trace element intakes /kg of exclusively-breast-fed infants at 1, 2 and 3 months of age respectively were: copper 0.075, 0.051 and 0.043 mg; iron 0.075, 0.055 and 0.048 mg; manganese 0.9, 0.6 and 0.5 μg; zinc 0.420, 0.215 and 0.150 mg. The latter values for Cu, Fe, and Zn intakes were in good agreement with earlier results, whereas the intake of Mn was lower. The intakes of trace elements by breast-fed infants seemed to be below the recommended dietary allowances (Food and Nutrition Board, 1973; WHO Expert Committee on Trace Elements in Human Nutrition, 1973).2. There seems to be no information on trace element concentrations of breast milk related to the energy content. Such values are therefore included for breast milk from Finnish women for the 1st 6 months of lactation.

The nutrition of meat-type ducks. 2. The effects of variation in the energy and protein contents of diets on biological performance and carcass characteristics

1982 ◽  
Vol 33 (5) ◽  
pp. 865 ◽  
Author(s):  
AP Siregar ◽  
RB Cumming ◽  
DJ Farrell
Keyword(s):  
Crude Protein ◽  
Energy Content ◽  
Maximum Growth ◽  
High Energy ◽  
Metabolizable Energy ◽  
Feed Conversion ◽  
Protein Ratio ◽  
Low Protein ◽  
Biological Performance ◽  
Good Agreement

In three experiments, ducklings aged 2 or 3 weeks were grown to 8 weeks of age on diets containing from 12 to 25 % crude protein, and from 11 .6 to 15.2 MJ metabolizable energy (ME)/kg 'as fed'. Generally the highest growth rates and best feed conversions were observed on diets with the highest energy content. A dietary protein content of about 12% was adequate for maximum growth, best feed conversion, and the highest protein efficiency ratio. Where comparison could be made, males grew faster than females. ME contents of the diet determined by total collection of excreta or its estimation using Cr2O3 were in good agreement. ME values for the diets declined as ducklings aged, as did nitrogen balance. Carcass protein decreased and carcass fat increased as the energy (kJ) to protein (%) ratio increased. Dressing percentage tended to increase with increasing dietary energy. Females had higher dressing percentages than males. It would appear that, for best growth rate and feed conversion, a low protein of 12-13 % and a high energy diet of about 14.0 MJ ME/kg, corresponding to an energy to protein ratio of about 1000, are adequate for ducks grown from 2 to 8 weeks. For maximum carcass lean, and minimum fat content, a low energy (kJ) to protein (%) ratio of about 600 is desirable. This corresponds to dietary concentrations of about 15 MJ/ME kg of diet and 24% crude protein.

scholarly journals Analysis of Quality Factor Enhancement in the Monolithic InGaN/GaN Nanorod Array

2019 ◽  
Vol 9 (7) ◽  
pp. 1295
Author(s):  
Chia-Yen Huang ◽  
Tzu-Ying Tai ◽  
Kuo-Bin Hong ◽  
Hao-Chung Kuo ◽  
Tien-Chang Lu
Keyword(s):  
Integrated Circuits ◽  
Quality Factor ◽  
Mode Selection ◽  
Building Blocks ◽  
Nanorod Array ◽  
Dominant Mode ◽  
Scattering Loss ◽  
Whispering Gallery ◽  
Rod Array ◽  
Good Agreement

Whispering gallery mode (WGM) lasers and resonators are key building blocks for photonic integrated circuits. The quality factor and resonant wavelength are strong functions of the cavity size. Nanoscale WGM cavities suffer from a low-quality factor due to prominent scattering loss. However, the quality factor could be enhanced by forming an optically-coupled rod array or photonic molecules. Through simulations, we revealed how rod-to-rod optical coupling influenced the threshold pumping level and dominant mode selection, where the trend showed good agreement with the experimental observation. According to the simulation, the quality factor could be enhanced by up to eight times by forming a six-rod photonic molecule. The quality factor and effective mode were both superior to the single rods with the same wafer device footprint.

scholarly journals A Mathematical Model to Investigate the Transmission of COVID-19 in the Kingdom of Saudi Arabia

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Fehaid Salem Alshammari
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Saudi Arabia ◽  
Reproduction Number ◽  
Real Data ◽  
Kingdom Of Saudi Arabia ◽  
Globally Stable ◽  
Disease Free ◽  
The Basic Reproduction Number ◽  
Good Agreement

Since the first confirmed case of SARS-CoV-2 coronavirus (COVID-19) on March 02, 2020, Saudi Arabia has not reported quite a rapid COVD-19 spread as seen in America and many European countries. Possible causes include the spread of asymptomatic COVID-19 cases. To characterize the transmission of COVID-19 in Saudi Arabia, a susceptible, exposed, symptomatic, asymptomatic, hospitalized, and recovered dynamical model was formulated, and a basic analysis of the model is presented including model positivity, boundedness, and stability around the disease-free equilibrium. It is found that the model is locally and globally stable around the disease-free equilibrium when R 0 < 1 . The model parameterized from COVID-19 confirmed cases reported by the Ministry of Health in Saudi Arabia (MOH) from March 02 till April 14, while some parameters are estimated from the literature. The numerical simulation showed that the model predicted infected curve is in good agreement with the real data of COVID-19-infected cases. An analytical expression of the basic reproduction number R 0 is obtained, and the numerical value is estimated as R 0 ≈ 2.7 .

scholarly journals Flow control of weakly non-parallel flows: application to trailing vortices

2017 ◽  
Vol 822 ◽  
pp. 342-363 ◽  
Author(s):  
F. Viola ◽  
E. Pezzica ◽  
G. V. Iungo ◽  
F. Gallaire ◽  
S. Camarri
Keyword(s):  
Flow Control ◽  
Flow Condition ◽  
Amplification Factor ◽  
Base Flow ◽  
Flow Dynamics ◽  
Inlet Flow ◽  
Flow Modification ◽  
Parallel Flows ◽  
Trailing Vortices ◽  
Sensitivity Map

A general formulation is proposed to control the integral amplification factor of harmonic disturbances in weakly non-parallel amplifier flows. The sensitivity of the local spatial stability spectrum to a base-flow modification is first determined, generalizing the results of Bottaro et al. (J. Fluid Mech., vol. 476, 2003, pp. 293–302). This result is then used to evaluate the sensitivity of the overall spatial growth to a modification of the inlet flow condition. This formalism is applied to a non-parallel Batchelor vortex, which is a well-known model for trailing vortices generated by a lifting wing. The resulting sensitivity map indicates the optimal modification of the inlet flow condition enabling the stabilization of the helical modes. It is shown that the control, formulated using a single linearization of the flow dynamics carried out on the uncontrolled configuration, successfully reduces the total spatial amplification of all convectively unstable disturbances.

Oscillator Strength Measurements in the Vacuum-Ultraviolet by the Emission Method

1988 ◽  
Vol 102 ◽  
pp. 353-356
Author(s):  
C. Goldbach ◽  
G. Nollez
Keyword(s):  
Oscillator Strength ◽  
Vacuum Ultraviolet ◽  
Oscillator Strengths ◽  
Emission Method ◽  
Absolute Scale ◽  
Good Agreement

AbstractThe principles and the realization of an experiment devoted to oscillator strength measurements in the vacuum-ultraviolet by the emission method are briefly presented. The results obtained for the strong multiplets of neutral nitrogen and carbon in the 1200-2000 Å range yield an absolute scale of oscillator strengths in good agreement with the most recent calculations.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

Diagnostic Value of Electron Microscopy in Soft Tissue Tumors

1970 ◽  
Vol 28 ◽  
pp. 220-221
Author(s):  
Gerald Fine ◽  
Azorides R. Morales
Keyword(s):  
Cardiac Myxoma ◽  
Osteogenic Sarcoma ◽  
Diagnostic Value ◽  
Soft Tissue Tumors ◽  
Amelanotic Melanoma ◽  
Growth Patterns ◽  
Light Microscopic Level ◽  
Mesenchymal Tumors ◽  
Good Agreement

For years the separation of carcinoma and sarcoma and the subclassification of sarcomas has been based on the appearance of the tumor cells and their microscopic growth pattern and information derived from certain histochemical and special stains. Although this method of study has produced good agreement among pathologists in the separation of carcinoma from sarcoma, it has given less uniform results in the subclassification of sarcomas. There remain examples of neoplasms of different histogenesis, the classification of which is questionable because of similar cytologic and growth patterns at the light microscopic level; i.e. amelanotic melanoma versus carcinoma and occasionally sarcoma, sarcomas with an epithelial pattern of growth simulating carcinoma, histologically similar mesenchymal tumors of different histogenesis (histiocytoma versus rhabdomyosarcoma, lytic osteogenic sarcoma versus rhabdomyosarcoma), and myxomatous mesenchymal tumors of diverse histogenesis (myxoid rhabdo and liposarcomas, cardiac myxoma, myxoid neurofibroma, etc.)

Photographic Equidensitometry of High Voltage Electron Images of Thick Noncrystalline Materials

1972 ◽  
Vol 30 ◽  
pp. 594-595
Author(s):  
Keinosuke Kobayashi
Keyword(s):  
High Voltage ◽  
Linear Response ◽  
Thickness Distribution ◽  
Contour Map ◽  
Mass Thickness ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Homogeneous Particle ◽  
Photographic Emulsions ◽  
Logarithmic Relation

Equidensitometry as developed by E. Lau and W. Krug has been little used in the analysis of ordinary electron photomicrographs, yet its application to the high voltage electron images proves merits of this procedure. Proper sets (families) of equidensities as shown in the next page are able to reveal the contour map of mass thickness distribution in thick noncrystalline specimens. The change in density of the electron micrograph is directly related to the mass thickness of corresponding area in the specimen, because of the linear response of photographic emulsions to electrons and the logarithmic relation between electron opacity and mass thickness of amorphous object.This linearity is verified by equidensitometry of a spherical solid object as shown in Fig. 1a. The object is a large (1 μ) homogeneous particle of polystyrene. Fig. 1b is a composite print of three equidensities of the 1st order prepared from Fig. 1a.

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