Nonlinear Faraday resonance in a box with a square base

1989 ◽  
Vol 209 ◽  
pp. 265-284 ◽  
Author(s):  
M. Nagata
Keyword(s):  
Surface Wave ◽  
Natural Frequency ◽  
Mixed Mode ◽  
Single Mode ◽  
Basins Of Attraction ◽  
Vertical Oscillation ◽  
Subcritical Region ◽  
Mixed Modes

Surface wave motions in a container with a square base, which is subject to a vertical oscillation, are considered when the amplitude of the oscillation is small and the frequency of the oscillation is close to twice the natural frequency of the system. Subcritical wave motions are found for single modes as well as mixed modes. Here, single modes are described by either one of the two horizontal coordinates whereas mixed modes depend on both coordinates. It is found that in some subcritical region a stable single mode and a stable mixed mode coexist, producing complex basins of attraction.

Diverse Models of Distance Teaching Universities

2011 ◽  
pp. 727-733 ◽  
Author(s):  
Sarah Guri-Rosenblit
Keyword(s):  
Continuing Education ◽  
Mixed Mode ◽  
Relevant Literature ◽  
Single Mode ◽  
Admission Policy ◽  
Distance Teaching ◽  
Organizational Models ◽  
Virtual Technology ◽  
Entry Requirements ◽  
Education Courses

Universities offering studies through distance teaching methods vary enormously in how they were initiated, the clienteles they aim to serve, how they are funded, and the kinds of programs they offer. Distance teaching at university level is provided currently through at least five major organizational models: Single-mode distance teaching universities; dual- and mixed-mode universities; extensions; consortia-type ventures; and virtual technology-based universities. Each of these models can be divided into additional sub-groups. The fully-fledged distance teaching universities, for instance, are treated in the relevant literature as a generic group, but differ from each other in many respects (Guri-Rosenblit, 1999). Some are operating as huge national universities, while others function on a limited provincial level. Few adopted an open admission policy, while most others require the same entry requirements as their conventional counterparts, etc. The dual- and the mixed-mode universities, as well as the consortia-type ventures, constitute nowadays the leading models of distance teaching provision. They operate in many national settings, and represent a rich composition of diverse higher education institutions, such as: research versus mainly teaching-oriented universities; large and small establishments; fully accredited or experimental in nature; offering mainly continuing education courses versus full academic degrees. However, this overview analyzes only the underlying premises of distance teaching in each of the five major models. Its scope does not allow discussing in detail the sub-groups contained in each model.

scholarly journals Transitions From Telephone Surveys to Self-Administered and Mixed-Mode Surveys: Aapor Task Force Report

2020 ◽  
Author(s):  
Kristen Olson ◽  
Jolene D Smyth ◽  
Rachel Horwitz ◽  
Scott Keeter ◽  
Virginia Lesser ◽  
...  
Keyword(s):  
Mixed Mode ◽  
Task Force ◽  
Response Rates ◽  
The Self ◽  
Empirical Literature ◽  
Self Administration ◽  
Task Force Report ◽  
Telephone Surveys ◽  
Mixed Modes ◽  
Survey Administration

Abstract Telephone surveys have been a ubiquitous method of collecting survey data, but the environment for telephone surveys is changing. Many surveys are transitioning from telephone to self-administration or combinations of modes for both recruitment and survey administration. Survey organizations are conducting these transitions from telephone to mixed modes with only limited guidance from existing empirical literature and best practices. This article summarizes findings by an AAPOR Task Force on how these transitions have occurred for surveys and research organizations in general. We find that transitions from a telephone to a self-administered or mixed-mode survey are motivated by a desire to control costs, to maintain or improve data quality, or both. The most common mode to recruit respondents when transitioning is mail, but recent mixed-mode studies use only web or mail and web together as survey administration modes. Although early studies found that telephone response rates met or exceeded response rates to the self-administered or mixed modes, after about 2013, response rates to the self-administered or mixed modes tended to exceed those for the telephone mode, largely because of a decline in the telephone mode response rates. Transitioning offers opportunities related to improved frame coverage and geographic targeting, delivery of incentives, visual design of an instrument, and cost savings, but challenges exist related to selecting a respondent within a household, length of a questionnaire, differences across modes in use of computerization to facilitate skip patterns and other questionnaire design features, and lack of an interviewer for respondent motivation and clarification. Other challenges related to surveying youth, conducting surveys in multiple languages, collecting nonsurvey data such as biomeasures or consent to link to administrative data, and estimation with multiple modes are also prominent.

scholarly journals Period spacings in red giants

2018 ◽  
Vol 618 ◽  
pp. A109 ◽  
Author(s):  
B. Mosser ◽  
C. Gehan ◽  
K. Belkacem ◽  
R. Samadi ◽  
E. Michel ◽  
...  
Keyword(s):  
Asymptotic Expansion ◽  
Stellar Evolution ◽  
Mixed Mode ◽  
Frequency Resolution ◽  
Red Giants ◽  
Large Set ◽  
Low Mass Stars ◽  
Mode Pattern ◽  
Low Mass ◽  
Mixed Modes

Context. Oscillation modes with a mixed character, as observed in evolved low-mass stars, are highly sensitive to the physical properties of the innermost regions. Measuring their properties is therefore extremely important to probe the core, but requires some care, due to the complexity of the mixed-mode pattern. Aims. The aim of this work is to provide a consistent description of the mixed-mode pattern of low-mass stars, based on the asymptotic expansion. We also study the variation of the gravity offset εg with stellar evolution. Methods. We revisit previous works about mixed modes in red giants and empirically test how period spacings, rotational splittings, mixed-mode widths, and heights can be estimated in a consistent view, based on the properties of the mode inertia ratios. Results. From the asymptotic fit of the mixed-mode pattern of a large set of red giants at various evolutionary stages, we derive unbiased and precise asymptotic parameters. As the asymptotic expansion of gravity modes is verified with a precision close to the frequency resolution for stars on the red giant branch (10−4 in relative values), we can derive accurate values of the asymptotic parameters. We decipher the complex pattern in a rapidly rotating star, and explain how asymmetrical splittings can be inferred. We also revisit the stellar inclinations in two open clusters, NGC 6819 and NGC 6791: our results show that the stellar inclinations in these clusters do not have privileged orientation in the sky. The variation of the asymptotic gravity offset with stellar evolution is investigated in detail. We also derive generic properties that explain under which conditions mixed modes can be observed.

Nonlinear interactions between the two wakes behind a pair of square cylinders

2014 ◽  
Vol 759 ◽  
pp. 295-320 ◽  
Author(s):  
J. Mizushima ◽  
G. Hatsuda
Keyword(s):  
Nonlinear Stability ◽  
Mixed Mode ◽  
Single Mode ◽  
Nonlinear Interactions ◽  
Symmetric Mode ◽  
Amplitude Equations ◽  
Equilibrium Solutions ◽  
Antisymmetric Mode ◽  
Weakly Nonlinear ◽  
Mode Solution

AbstractNonlinear interactions between the two wakes behind a pair of square cylinders, which are placed side by side in a uniform flow, are investigated by the linear and weakly nonlinear stability analyses and numerical simulations. It is known from the linear stability analysis that the flow past a pair of cylinders becomes unstable to a symmetric or an antisymmetric mode of disturbance, depending on the gap ratio, the ratio of the gap distance between the two cylinders to the cylinder diameter. The antisymmetric mode gives the critical condition for smaller gap ratios than a threshold value, and for larger gap ratios the symmetric mode becomes the most unstable. We focus on the flow pattern arising through the nonlinear interactions of the two modes of disturbance for gap ratios around the threshold value when both modes are growing. We derive a couple of amplitude equations for the two modes to properly describe the nonlinear interaction between them by applying the weakly nonlinear stability theory. The amplitude equations are shown to have three equilibrium solutions except the null solution such as a mixed-mode solution, symmetric and antisymmetric single-mode solutions. Examination of the stability of each equilibrium solution leads to a conclusion that the mixed-mode solution exchange its stability with both the symmetric and the antisymmetric single-mode solutions simultaneously. In the case where the mixed-mode solution is stable, both the symmetric and antisymmetric modes have finite amplitudes, and the resultant flow has an asymmetric flow pattern comprising of finite amplitudes of the two modes of disturbance superposed on the steady symmetric flow. While in the case where both the single-mode solutions are stable, either of the symmetric- and antisymmetric-mode solutions survives, overwhelming the other. Then, if the symmetric mode attains at an equilibrium finite amplitude and the antisymmetric mode vanishes, the resultant flow is symmetric, and if the antisymmetric mode survives and the symmetric mode decays out, the flow becomes asymmetric with the antisymmetric mode of disturbance superposed on the steady symmetric flow. Thus, the flow appearing due to instability differs depending on the initial condition, not uniquely determined, when both single-mode solutions are stable. We numerically delineated the region in the parameter space of the gap ratio and the Reynolds number where the mixed-mode solution is stable. The theoretical results obtained from the weakly nonlinear stability analyses are confirmed by numerical simulations. The conclusion derived from the stability analysis of the equilibrium solutions of the amplitude equations is widely applicable also to other double Hopf bifurcation problems.

scholarly journals A Geometric Barycenter-Based Clutter Suppression Method for Ship Detection in HF Mixed-Mode Surface Wave Radar

2019 ◽  
Vol 11 (9) ◽  
pp. 1141
Author(s):  
Jiazhi Zhang ◽  
Xin Zhang ◽  
Weibo Deng ◽  
Lei Ye ◽  
Qiang Yang
Keyword(s):  
Surface Wave ◽  
Mixed Mode ◽  
Training Data ◽  
Matrix Estimation ◽  
Ship Detection ◽  
Practical System ◽  
Training Samples ◽  
Wave Radar ◽  
Dimension Space ◽  
Space Time Adaptive Processing

The nonhomogeneous clutter is a major challenge for ship detection in high-frequency mixed-mode surface wave radar. In this paper, a geometric barycenter-based reduced-dimension space-time adaptive processing method is proposed to suppress the clutter. Given the measured dataset, the range correlation of sea clutter is first investigated. Then, joint domain localized processing is applied to solve the training samples starve scenario in a practical system. The geometric barycenter-based training data selector is presented to select valid training samples and improve the accuracy of the clutter covariance matrix estimation. Finally, the validity of the proposed method is verified using the experimental data and the results show that it outperforms the conventional method in the nonhomogeneous environment of a practical system.

scholarly journals Progressive delamination analysis through two-way global-local coupling approach preserving energy dissipation for single-mode and mixed-mode loading

2019 ◽  
Vol 223 ◽  
pp. 110892 ◽  
Author(s):  
Margarita Akterskaia ◽  
Pedro P. Camanho ◽  
Eelco Jansen ◽  
Albertino Arteiro ◽  
Raimund Rolfes
Keyword(s):  
Energy Dissipation ◽  
Mixed Mode ◽  
Single Mode ◽  
Mixed Mode Loading ◽  
Coupling Approach ◽  
Local Coupling

Die richtige Mischung? Ein randomisiertes Experiment zur Datenqualität bei der Kombination von Telefon- und Onlineerhebung in der empirischen Sozialforschung

2017 ◽  
Vol 46 (2) ◽  
pp. 89-106 ◽  
Author(s):  
Gerhard Krug ◽  
Johann Carstensen ◽  
Peter Kriwy
Keyword(s):  
Mixed Mode ◽  
Single Mode ◽  
Negative Effekte

Zusammenfassung:Der Beitrag untersucht die Datenqualität einer kombinierten Telefon- und Onlinebefragung. Solche Mixed-Mode-Designs werden in der deutschen akademischen Sozialforschung noch relativ selten eingesetzt, obwohl damit eine Reihe von Vorteilen verbunden sein kann. Allerdings können sich auch negative Effekte aus einer Kombination von Daten aus verschiedenen Quellen ergeben. Im Rahmen eines randomisierten Experimentes werden eine Single-Mode-Telefonbefragung und eine Mixed-Mode-Telefon-/Onlinebefragung hinsichtlich mehrerer Indikatoren der Datenqualität untersucht. Vorteilhafte Effekte zeigt die Mixed-Mode-Erhebung bezüglich einer erhöhten Responserate. Zudem liegen die soziodemographischen Merkmale der Befragten näher an der Grundgesamtheit und Antworten auf sensitive Fragen weisen geringere Messfehler auf. Andererseits erhöht sich die Antwortverweigerung, allerdings nur unter sehr spezifischen (und vermeidbaren) Bedingungen.

scholarly journals Improved seismic profiling by minimally invasive multimodal surface wave method with standard penetration test source (MMSW-SPT)

2016 ◽  
Vol 208 (3) ◽  
pp. 1308-1312 ◽  
Author(s):  
Shibin Lin ◽  
Jeramy C. Ashlock
Keyword(s):  
Surface Wave ◽  
Minimally Invasive ◽  
Single Mode ◽  
Standard Penetration Test ◽  
Wave Method ◽  
Penetration Test ◽  
Testing Methods ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Surface Wave Method

Abstract Surface waves propagating in layered media inherently possess multimodal dispersion characteristics. However, traditional surface wave testing methods employing measurements at the free surface usually capture only a single apparent dispersion curve, especially when using short geophone arrays common to near surface and geotechnical-scale investigations. Such single-mode or fragmented multimode apparent dispersion curves contain only a fraction of the possible dispersion information, thus limiting the accuracy of inverted profiles. To enable more robust measurement of higher Rayleigh-wave modes, a recently developed hybrid minimally invasive multimodal surface wave method is combined herein with the widely used geotechnical standard penetration test (SPT), which is employed as a practical and ubiquitous downhole source. Upon superimposing surface wave dispersion data for a range of SPT impact depths within the soil, higher modes can be measured more consistently and reliably relative to traditional non-invasive testing methods. As a result, misidentification of multiple dispersion modes can be practically eliminated, significantly improving the accuracy and certainty of inversion results.

Exploiting surface consistency for surface-wave characterization and mitigation — Part 1: Theory and 2D examples

Geophysics ◽  
2017 ◽  
Vol 82 (1) ◽  
pp. V21-V37 ◽  
Author(s):  
Christine E. Krohn ◽  
Partha S. Routh
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Single Mode ◽  
Complex Surface ◽  
Companion Paper ◽  
Inversion Method ◽  
Earth Model ◽  
Model Parameters ◽  
Quality Factors ◽  
Near Surface

We have developed a new tomographic inversion method that is able to determine the properties of complex surface waves, which are multimodal and heterogeneous. These properties can be used to generate a detailed near-surface earth model or to predict and remove the surface waves, while protecting reflection signals even with aliased data. The inversion assumes plane-wave physics and generates surface-consistent model parameters as a function of frequency. In this paper, we validate our method with 2D models and data. In a companion paper, we demonstrate its application to 3D data. Inversion for a single mode is linear, but the linearity does not hold at higher frequencies, where multiple modes interfere. However, single-mode inversion results can be used to create a starting model for the subsequent nonlinear multimode tomography. The resulting velocity-frequency grid has greater resolution compared with a beam-forming method. The dispersion curves can be used as input to a subsequent standard 1D surface-wave inversion to generate a velocity-depth model. The tomographic method also determines a grid of attenuation quality factors and variations in the source amplitude and bandwidth, which correlate with the near-surface elevation changes. The amplitude and phase properties can be used together to predict the surface-wave waveforms, which can then be adaptively subtracted from the data on a trace-to-trace basis.

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