Oceanic Frontogenesis

2021 ◽  
Vol 13 (1) ◽  
pp. 227-253
Author(s):  
James C. McWilliams
Keyword(s):  
Positive Feedback ◽  
Turbulent Mixing ◽  
Secondary Circulation ◽  
Horizontal Velocity ◽  
Future Research ◽  
Density Gradients ◽  
Feedback Process ◽  
Dynamical Processes ◽  
System Functioning ◽  
Frontal Instability

Frontogenesis is the fluid-dynamical processes that rapidly sharpen horizontal density gradients and their associated horizontal velocity shears. It is a positive feedback process where the ageostrophic, overturning secondary circulation in the cross-front plane accelerates the frontal sharpening until an arrest occurs through frontal instability and other forms of turbulent mixing. Several well-known types of oceanic frontal phenomena are surveyed, their impacts on oceanic system functioning are assessed, and future research is envisioned.

A Positive Feedback Process Related to the Rapid Development of an Extratropical Cyclone over the Kuroshio/Kuroshio Extension

2018 ◽  
Vol 146 (2) ◽  
pp. 417-433 ◽  
Author(s):  
Hidetaka Hirata ◽  
Ryuichi Kawamura ◽  
Masaya Kato ◽  
Taro Shinoda
Keyword(s):  
Water Vapor ◽  
Positive Feedback ◽  
Heat Supply ◽  
Rapid Development ◽  
Kuroshio Extension ◽  
Heat Fluxes ◽  
Latent Heating ◽  
Sensible Heat ◽  
Feedback Process ◽  
The Kuroshio

Abstract The active roles of sensible heat supply from the Kuroshio/Kuroshio Extension in the rapid development of an extratropical cyclone, which occurred in the middle of January 2013, were examined by using a regional cloud-resolving model. In this study, a control experiment and three sensitivity experiments without sensible and latent heat fluxes from the warm currents were conducted. When the cyclone intensified, sensible heat fluxes from these currents become prominent around the cold conveyor belt (CCB) in the control run. Comparisons among the four runs revealed that the sensible heat supply facilitates deepening of the cyclone’s central pressure, CCB development, and enhanced latent heating over the bent-back front. The sensible heat supply enhances convectively unstable conditions within the atmospheric boundary layer along the CCB. The increased convective instability is released by the forced ascent associated with frontogenesis around the bent-back front, eventually promoting updraft and resultant latent heating. Additionally, the sensible heating leads to an increase in the water vapor content of the saturated air related to the CCB through an increase in the saturation mixing ratio. This increased water vapor content reinforces the moisture flux convergence at the bent-back front, contributing to the activation of latent heating. Previous research has proposed a positive feedback process between the CCB and latent heating over the bent-back front in terms of moisture supply from warm currents. Considering the above two effects of the sensible heat supply, this study revises the positive feedback process.

scholarly journals Analysis of one-dimensional models for exchange flows under strong stratification

2019 ◽  
Vol 70 (1) ◽  
pp. 41-56
Author(s):  
Steven J. Kaptein ◽  
Koen J. van de Wal ◽  
Leon P. J. Kamp ◽  
Vincenzo Armenio ◽  
Herman J. H. Clercx ◽  
...  
Keyword(s):  
Density Gradient ◽  
Turbulent Mixing ◽  
Schmidt Number ◽  
Density Gradients ◽  
One Dimensional ◽  
Exchange Flows ◽  
Dimensional Models ◽  
The One ◽  
Horizontal Density Gradient ◽  
Classical Constant

AbstractOne-dimensional models of exchange flows driven by horizontal density gradients are well known for performing poorly in situations with weak turbulent mixing. The main issue with these models is that the horizontal density gradient is usually imposed as a constant, leading to non-physically high stratification known as runaway stratification. Here, we propose two new parametrizations of the horizontal density gradient leading to one-dimensional models able to tackle strongly stratified exchange flows at high and low Schmidt number values. The models are extensively tested against results from laminar two-dimensional simulations and are shown to outperform the models using the classical constant parametrization for the horizontal density gradients. Four different flow regimes are found by exploring the parameter space defined by the gravitational Reynolds number Reg, the Schmidt number Sc, and the aspect ratio of the channel Γ. For small values of RegΓ, when diffusion dominates, all models perform well. However, as RegΓ increases, two clearly distinct regimes emerge depending on the Sc value, with an equally clear distinction of the performance of the one-dimensional models.

A Systematic Mapping on the Learning Analytics Field and Its Analysis in the Massive Open Online Courses Context

2015 ◽  
Vol 13 (3) ◽  
pp. 1-24 ◽  
Author(s):  
Barbara Moissa ◽  
Isabela Gasparini ◽  
Avanilde Kemczinski
Keyword(s):  
Learning Analytics ◽  
Online Courses ◽  
Massive Open Online Courses ◽  
Future Research ◽  
Systematic Mapping Study ◽  
Mapping Study ◽  
Data Types ◽  
Massive Open Online ◽  
Systematic Mapping ◽  
Dynamical Processes

Learning Analytics (LA) is a field that aims to optimize learning through the study of dynamical processes occurring in the students' context. It covers the measurement, collection, analysis and reporting of data about students and their contexts. This study aims at surveying existing research on LA to identify approaches, topics, and needs for future research. A systematic mapping study is launched to find as much literature as possible. The 127 papers found (resulting in 116 works) are classified with respect to goals, data types, techniques, stakeholders and interventions. Despite the increasing interest in field, there are no studies relating it to the Massive Open Online Courses (MOOCs) context. The goal of this paper is twofold, first we present the systematic mapping on LA and after we analyze its findings in the MOOCs context. As results we provide an overview of LA and identify perspectives and challenges in the MOOCs context.

AMPLIFICATION OF UTEROGLOBIN SECRETION BY ALTERNATING PROLACTIN-PROGESTERONE ADMINISTRATION

1989 ◽  
Vol 122 (3) ◽  
pp. R5-R6 ◽  
Author(s):  
J. C. Daniel ◽  
S. C. June ja
Keyword(s):  
Positive Feedback ◽  
Feedback Process ◽  
Study Support

ABSTRACT Long-term ovariectomized rabbits were given injections of progesterone and prolactin in an alternating sequence (progesterone for 5 days, prolactin for 4 days and progesterone for 5 days) to test the hypothesis that each of these hormones acts to increase the other's receptor, resulting in a positive feedback process whereby prolactin augments the progesterone-dependent increase in the mRNA for the uterine protein, uteroglobin. The results of this study support the hypothesis, in that the experimental rabbits produced exceptionally large concentrations of uteroglobin.

scholarly journals Attitudes of Saudi EFL Female Students Towards Current Teacher Feedback Practices

2021 ◽  
Vol 11 (6) ◽  
pp. 90
Author(s):  
Khaled Aldossary
Keyword(s):  
Foreign Language ◽  
Positive Feedback ◽  
Female Students ◽  
Quantitative Approach ◽  
Teacher Feedback ◽  
Future Research ◽  
Efl Learners ◽  
Efl Students ◽  
Current Practices

This study aimed to investigate the attitudes of female Saudi English as a foreign language (EFL) learners towards the current practices and the challenges of teacher feedback. Utilizing a quantitative approach, 87 female Saudi EFL students completed a questionnaire about their experience with teacher feedback and the problems they encountered with this during the semester. The study aimed to explore two main aspects, including the students’ attitudes towards the current practices of teacher feedback and the challenges encountered, and the students’ suggestions for improving teacher feedback practices. The study outcomes revealed that the students receive direct and positive feedback. Additionally, the students perceived the teachers’ feedback to be useful and of good quality. The findings also indicated that students expect and prefer detailed feedback on their written tasks. However, the participants reported some concerns regarding the punctuality of teacher feedback and provided suggestions to improve such practices. The study also presents the limitations and recommendations for future research.

Conditions for the Compost Bomb Instability

2020 ◽  
Author(s):  
Joe Clarke ◽  
Paul Ritchie ◽  
Peter Cox
Keyword(s):  
Global Warming ◽  
Positive Feedback ◽  
Land Surface ◽  
Microbial Respiration ◽  
Land Surface Model ◽  
Surface Model ◽  
Specific Rate ◽  
Feedback Process ◽  
Moss Layer ◽  
Soil Temperatures

<p>Under global warming, soil temperatures are expected to rise. This increases the specific rate of microbial respiration in the soils which in turn warms the soil, creating a positive feedback process. This leads to the possibility of an instability, known as the compost bomb, in which rapidly warming soils release their soil carbon as CO2 to the atmosphere, accelerating global warming. Models of the compost bomb have exhibited interesting dynamical phenomena: excitability, rate induced tipping and bifurcation induced tipping. We examine models with increasing degrees of sophistication, to help understand the conditions that give rise to the compost bomb. We clarify the role an insulating moss layer plays and demonstrate that it has a 'most dangerous' thickness. We also use JULES, a land surface model, to examine where a compost bomb might occur and what affect other processes such as hydrology might have on the compost bomb.</p>

scholarly journals Attention Drifting In and Out: The Boredom Feedback Model

2021 ◽  
pp. 108886832110102
Author(s):  
Katy Y. Y. Tam ◽  
Wijnand A. P. van Tilburg ◽  
Christian S. Chan ◽  
Eric R. Igou ◽  
Hakwan Lau
Keyword(s):  
Dynamic Process ◽  
Process Model ◽  
Feedback Loop ◽  
Cognitive Appraisals ◽  
Self Control ◽  
Future Research ◽  
Feedback Process ◽  
Feedback Model ◽  
Attentional Engagement ◽  
How People Learn

We synthesize established and emerging research to propose a feedback process model that explicates key antecedents, experiences, and consequences of the emotion boredom. The proposed Boredom Feedback Model posits that the dynamic process of boredom resembles a feedback loop that centers on attention shifts instigated by inadequate attentional engagement. Inadequate attentional engagement is a discrepancy between desired and actual levels of attentional engagement and is a product of external and internal influences, reflected in objective resources and cognitive appraisals. The model sheds light on several essential yet unresolved puzzles in the literature, including how people learn to cope with boredom, how to understand the relation between self-control and boredom, how the roles of attention and meaning in boredom can be integrated, why boredom is associated with both high- and low-arousal negative emotions, and what contributes to chronic boredom. The model offers testable hypotheses for future research.

Solidification of Pure Liquids and Liquid Mixtures Inside Ducts and Over External Bodies

1994 ◽  
Vol 47 (12) ◽  
pp. 589-621 ◽  
Author(s):  
Shoichiro Fukusako ◽  
Masahiko Yamada
Keyword(s):  
Binary Systems ◽  
Transport Phenomena ◽  
Fluid Motion ◽  
Liquid Mixtures ◽  
Transport Processes ◽  
Future Research ◽  
Density Gradients ◽  
Research Needs ◽  
Recent Advances ◽  
Pure Substances

Recent advances in the understanding of transport phenomena during solidification inside ducts and over external bodies are discussed. The emphasis is on fundamental aspects of the phenomena observed in transport processes during solidification. After a discussion of the solidification of pure substances, transport processes during solidification of binary systems are reviewed. The important role played by fluid motion owing to density gradients is also discussed and future research needs are assessed.

scholarly journals Family conflict, autonomic nervous system functioning, and child adaptation: State of the science and future directions

2011 ◽  
Vol 23 (2) ◽  
pp. 703-721 ◽  
Author(s):  
Mona El-Sheikh ◽  
Stephen A. Erath
Keyword(s):  
Nervous System ◽  
Autonomic Nervous System ◽  
Family Conflict ◽  
Future Research ◽  
Risk And Resilience ◽  
Autonomic Nervous ◽  
Wide Range ◽  
Psychological Maladjustment ◽  
System Functioning ◽  
State Of The Science

AbstractThe family is one of the primary contexts of child development. Marital and parent–child conflict (family conflict) are common and predict a wide range of negative behavioral and emotional outcomes in children. Thus, an important task for developmental researchers is to identify the processes through which family conflict contributes to children's psychological maladjustment, as well as vulnerability and protective factors in the context of family conflict. In the current paper, we aim to advance a conceptual model that focuses on indices of children's autonomic nervous system (ANS) functioning that increase vulnerability or provide protection against psychological maladjustment in the context of family conflict. In doing so, we provide a selective review that reflects the state of the science linking family conflict, children's ANS activity, and child psychological adjustment, and offer directions and guidance for future research. Our hope is to accelerate research at the intersection of family conflict and ANS functioning to advance understanding of risk and resilience among children.

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