scholarly journals Long-term increase in crustacean zooplankton abundance in the southern Benguela upwelling region (1951–1996): bottom-up or top-down control?

1998 ◽  
Vol 55 (4) ◽  
pp. 803-807 ◽  
Author(s):  
H Verheye
Keyword(s):  
Crustacean Zooplankton ◽  
Zooplankton Abundance ◽  
Top Down ◽  
Bottom Up ◽  
Benguela Upwelling

Dealing with Multiple Models in System Dynamics

2014 ◽  
Vol 3 (4) ◽  
pp. 17-35 ◽  
Author(s):  
Willem L. Auping ◽  
Erik Pruyt ◽  
Jan H. Kwakkel
Keyword(s):  
System Dynamics ◽  
Simulation Models ◽  
Dynamics Simulation ◽  
Multiple Models ◽  
Top Down ◽  
Bottom Up ◽  
New Approach ◽  
Behavioural Patterns ◽  
Copper Availability

This paper introduces an approach to compare simulation runs from multiple System Dynamics simulation models. Three dynamic hypotheses regarding the uncertain evolutions of long-term copper availability are introduced and used to illustrate the new approach. They correspond to three different perspectives on the copper system (global top-down, global bottom-up, and regional top-down). Although each of these models allows to generate a wealth of behavioural patterns, the focus in this paper is on the differences in trajectories caused by different models for identical values of shared parameters and identical settings of other assumptions, not on differences in behavioural patterns caused by each of the models. Hence, differences in trajectories between the three models are identified, quantified, and classified based on a quantified measure of difference. For these models, small differences between the trajectories are only found in stable runs, while the alternative perspectives are largely responsible for medium to large differences. Hence, it is concluded that multiple dynamic hypotheses may have to be modelled when dealing with uncertain issues.

Key factors affecting long-term penetration of global onshore wind energy integrating top-down and bottom-up approaches

2016 ◽  
Vol 85 ◽  
pp. 19-30 ◽  
Author(s):  
Hancheng Dai ◽  
Diego Silva Herran ◽  
Shinichiro Fujimori ◽  
Toshihiko Masui
Keyword(s):  
Wind Energy ◽  
Key Factors ◽  
Top Down ◽  
Bottom Up ◽  
Onshore Wind ◽  
Factors Affecting

e-Den goes down under

2017 ◽  
Vol 8 (1) ◽  
pp. 34-35
Author(s):  
Paul Brunton
Keyword(s):  
Undergraduate Education ◽  
Dental Education ◽  
Daily Basis ◽  
Dental School ◽  
Top Down ◽  
Self Directed Learning ◽  
Bottom Up ◽  
Directed Learning ◽  
The Way

Change is a constant in our profession, and we are familiar with this on a daily basis, as we constantly change how we practise. But consider how the way we learn and the very structure of our profession has changed in recent years. If I think back, I attended a traditional dental school and had, in my view, an excellent undergraduate education. Compare that top-down approach to the approach today, with its self-directed learning and student-led clinics – to give a couple of examples of a bottom-up model of providing effective dental education. The net result of this, in my view, is that today’s graduates are a little different in many respects, both when they graduate and in their long-term career ambitions.

Style-Dependency of Melodic Expectation

2015 ◽  
Vol 33 (1) ◽  
pp. 110-128 ◽  
Author(s):  
Zuzana Cenkerová ◽  
Richard Parncutt
Keyword(s):  
Learning Process ◽  
Auditory Scene Analysis ◽  
Scene Analysis ◽  
Top Down ◽  
Bottom Up ◽  
Gestalt Principles ◽  
Auditory Scene ◽  
Similar Organization ◽  
Melodic Expectation

In theories of auditory scene analysis and melodic implication/realization, melodic expectation results from an interaction between top-down processes (assumed to be learned and schema-based) and bottom-up processes (assumed innate, based on Gestalt principles). If principles of melodic expectation are partly acquired, it should be possible to manipulate them – to condition listeners' expectations. In this study, the resistance of three bottom-up expectation principles to learning was tested experimentally. In Experiment 1, expectations for stepwise motion (pitch proximity) were manipulated by conditioning listeners to large melodic leaps; preference for small intervals was reduced after a brief exposure. In Experiment 2, expectations for leaps to rise and steps to fall (step declination) were manipulated by exposing listeners to melodies comprising rising steps and falling leaps; this reduced preferences for descending seconds and thirds. Experiment 3 did not find and hence failed to alter the expectation for small intervals to be followed by an interval in the same direction (step inertia). The results support the theory that bottom-up principles of melodic perception are partly learned from exposure to pitch patterns in music. The long-term learning process could be reinforced by exposure to speech based on similar organization principles.

scholarly journals REASSESSMENT OF UNCERTAINTY EXPANSION BY LINEAR ADDITION OF LONG-TERM COMPONENTS FROM TOP-DOWN INFORMATION

Radiocarbon ◽  
2021 ◽  
pp. 1-15
Author(s):  
G Salazar ◽  
S Szidat
Keyword(s):  
Mass Spectrometry ◽  
Measurement Uncertainty ◽  
High Precision ◽  
Accelerator Mass Spectrometry ◽  
Expanded Uncertainty ◽  
Top Down ◽  
Bottom Up ◽  
Linear Addition

ABSTRACT Since radiocarbon accelerator mass spectrometry (14C AMS) is considered a high-precision technique, reassessment of the measurement uncertainty has been a topic of interest. Scientists from analytical and metrological fields have developed the top-down and bottom-up measurement of uncertainty approaches. The 14C quoted error should approximate the uncertainty of long-term repetitions of the top-down approach in order to be realistic. The novelty of this paper is that the uncertainty of both approaches were approximated to each other. Furthermore, we apportioned the graphitization, instrumentation, and bias components in order to additively expand the quoted error. Our results are comparable to error multipliers and to long-term repeatability studies reported by other laboratories. Our laboratory was established in late 2012 with N2 as stripper gas and 7 years later, we changed to helium stripper. Thus, we were able to compare both gases, and demonstrate that helium is a better stripper gas. In absolute F14C units, the ranges of graphitization+bias combined uncertainties were (0.7 to 4.1) × 10–3 for N2 and (0.7–3.0) × 10–3 for He depending on the standard 14C content. The error multiplier for He defined as the expanded uncertainty over quoted error, in average, was 1.7; while without the bias, the multiplier was 1.3.

Trends in Scenario Development Methodologies and Integration in NUMO’s Approach

2010 ◽  
Author(s):  
Takeshi Ebashi ◽  
Katsuhiko Ishiguro ◽  
Keiichiro Wakasugi ◽  
Hideki Kawamura ◽  
Irina Gaus ◽  
...  
Keyword(s):  
Safety Assessment ◽  
International Workshop ◽  
Assessment Process ◽  
Scenario Development ◽  
Top Down ◽  
Initial State ◽  
Bottom Up ◽  
Starting Point ◽  
Consistent Treatment

The development of scenarios for quantitative or qualitative analysis is a key element of the assessment of the safety of geological disposal systems. As an outcome of an international workshop attended by European and the Japanese implementers, a number of features common to current methodologies could be identified, as well as trends in their evolution over time. In the late nineties, scenario development was often described as a bottom-up process, whereby scenarios were said to be developed in essence from FEP databases. Nowadays, it is recognised that, in practice, the approaches actually adopted are better described as top-down or “hybrid”, taking as their starting point an integrated (top-down) understanding of the system under consideration including uncertainties in initial state, sometimes assisted by the development of “storyboards”. A bottom-up element remains (hence the term “hybrid”) to the extent that FEP databases or FEP catalogues (including interactions) are still used, but the focus is generally on completeness checking, which occurs parallel to the main assessment process. Recent advances focus on the consistent treatment of uncertainties throughout the safety assessment and on the integration of operational safety and long term safety.

scholarly journals Sustainable Rural Governance: How Rural Elections in China Lead to Long-Term Social Stability?

2019 ◽  
Vol 11 (22) ◽  
pp. 6196
Author(s):  
Jinrui Xi ◽  
Feng Wen
Keyword(s):  
Rural China ◽  
Chinese Government ◽  
Social Stability ◽  
Collective Actions ◽  
Top Down ◽  
Public Goods Provision ◽  
Bottom Up ◽  
Rural Governance ◽  
Timely Fashion

Government inspections are a typical approach that the Chinese government adopts in executing its policy agenda and propagating its ideological ideals. However, top-down administrative imperatives as such tend to be consuming in resources and less effective in actual governance. They are not necessarily the most sustainable means to ensure efficient governance in the long term. Bottom-up self-governance in rural China, on the other hand, provides the essential mechanism for sustainable governance. In this paper we study one of these bottom-up self-governance approaches in China—rural elections. We propose that, via three distinctive mechanisms, rural elections in China serve as a stabilizer for the entire state and fill the loopholes that top-down government inspections potentially allow. Specifically, we argue that individuals with electoral experiences are less likely to engage in protests, or other forms of collective actions, than those without. This effect holds in that, first, elections improve public goods provision in rural China; second, voters’ personal experience in elections changes their perception of the Chinese regime from being authoritarian to being benevolent and caring; third, elections expose the Chinese regime to emerging social dissent in a timely fashion that allows for self-correction. This theoretical prescription receives strong empirical, statistical analysis using the latest Asian Barometer Survey (ABS 2014) dataset.

scholarly journals Response of mycorrhizae to herbivory and soil moisture in a semiarid grazing ecosystem

2020 ◽  
Author(s):  
Yadugiri V Tiruvaimozhi ◽  
Sumanta Bagchi ◽  
Mahesh Sankaran
Keyword(s):  
Water Availability ◽  
Host Species ◽  
Abiotic Factors ◽  
Tissue Loss ◽  
Annual Precipitation ◽  
Top Down ◽  
Short Term ◽  
Bottom Up ◽  
Irrigation Treatments

AbstractArbuscular mycorrhizal fungal (AMF) symbioses with plants can be influenced by top-down forces such as grazing, and also by bottom-up forces such as soil resource availability, both of which are being altered by anthropogenic and global change drivers. While the influence of each of these factors on AMF symbioses has been widely studied, explicit tests of the relative strengths of top-down versus bottom-up influences on these ubiquitous plant root symbioses are few. We studied AMF colonization responses of four species of graminoids (3 grasses Elymus longae-aristatus, Leymus secalinus and Stipa orientalis, and a sedge Carex melanantha) common to semiarid high-altitude rangelands of the Spiti region, Trans-Himalaya, to changes in a top-down driver, grazing intensity (through short-term clipping and long-term grazer exclusion experiments), and a bottom-up driver, water availability (using irrigation treatments, and by evaluating responses to annual precipitation levels across years). Over three years, AMF colonization in all four host species was influenced by precipitation, with the highest and lowest AMF colonization levels corresponding to years with the lowest and highest rainfall, respectively. However, responses to long-term grazer exclusion differed among host species, and across years: while some species showed decreases in AMF colonization levels under grazing, others showed increases from ungrazed control levels, and these responses changed, even reversed, across years. Responses to short-term clipping and irrigation treatments also differed among hosts, with some species responding to irrigation alone, some to clipping and irrigation combined, and others showing no changes in AMF colonization from control levels in any of the treatments. In our study, long-term changes in water availability influenced AMF colonization levels, while short-term responses were host specific. Responses to above-ground tissue loss, however, differed among host species both in the long- and short-term. Overall, this study demonstrates that while AMF colonization levels correspond to annual precipitation levels in this semiarid ecosystem, host species also play a role in influencing plant-AMF interactions in these rangelands, with colonization levels and responses to abiotic factors changing with host species.

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