Synchronization and Pattern Formation in a Memristive Diffusive Neuron Model

2021 ◽  
Vol 31 (11) ◽  
pp. 2130030
Author(s):  
Sanjeev Kumar Sharma ◽  
Arnab Mondal ◽  
Argha Mondal ◽  
Ranjit Kumar Upadhyay ◽  
Jun Ma
Keyword(s):  
Pattern Formation ◽  
Neuron Model ◽  
Gaussian White Noise ◽  
Coupled Systems ◽  
Global Network ◽  
Network Architectures ◽  
Hopf Bifurcation Point ◽  
Mixed Mode Oscillations ◽  
Spatial System ◽  
The Impact

In this article, we construct an excitable memristive diffusive neuron model by considering a biophysical slow–fast bursting oscillator and study the effects of electromagnetic induction on the dynamics of the single model as well as the coupled systems. We explore various firing regimes such as tonic spiking, bursting, and mixed-mode oscillations depending on the bifurcation structure with different injected current stimuli, then perform a comparative analysis on the synchronization of the coupled oscillators by setting the model into two different network architectures. First, a diffusively coupled network is considered, and later a global network is constructed. The results suggest that the diffusively connected neurons show complete synchronization at higher couplings for bursting and tonic spiking regimes. Furthermore, we show that the extended spatial system can generate spiral-like patterns in the vicinity of a Hopf bifurcation point and observe the impact of Gaussian white noise to study its effects on pattern formation. These types of patterns are robust in the excitable model. Our results might contribute significantly to the dynamical studies of irregular neural computation.

Disaster impacts in a port-city; learning from Beirut's  Port explosion

2021 ◽  
Author(s):  
Steluta topalov
Keyword(s):  
Large Scale ◽  
Focal Point ◽  
Transportation System ◽  
The Philippines ◽  
Lessons Learned ◽  
Social Dimension ◽  
Global Network ◽  
Port Cities ◽  
Residential Units ◽  
The Impact

<p>On 4 august 2020, one of the biggest non-nuclear explosions the world has seen in recent times took place in the Port of Beirut. Caused by the detonation of 2,750 tons of ammonium nitrate, inadequate stored in a warehouse in the port, the blast destroyed much of the city’s port and the surrounding infrastructure and severly  damaged the dense residential and commercial areas within 5 km of the explosion site. The impact of the explosion, which registered as a 3.3 magnitude earthquake according to the U.S. Geological Survey, was felt as far away as the island of Cyprus.</p><p>Athough the event was an technological hazard, the impact of the explosion is similar to a standardised natural disaster.</p><p>According to UNDP, a total of 200 000 residential units were affected with an estimated of 40 000 buildings damaged; 200 people lost their lives, around 6 000 individuals were injuried and around 300 000 people were displaced.</p><p>Such figure are comparable to other large-scale disasters such as Cyclone Vayu in India, which occured in June 2019 or the displacement caused by the Typhoon Vongfong, in the Philippines.</p><p>The frequent increase of the natural disasters  puts pressure on the critical infrastructure of the cities. The disruption of the transportation system,  which is vital for the sustainable daily operations, are having a big impact on the economical, enviromental and social dimension of a city system. Among the various types of transportation system, ports are a focal point because of its strategic role for the economic growth of cities,regions and  global network. In addition, they are nodal points for the social and economical activity of the inhabitants.</p><p>Although the ports have played a key role in the development of their host cities, they are also vulnerable to a broad range of risks and threats because of a particular spatial character: the location at the intersection of land and sea.  </p><p>The study of the Beirut’s Port explosion examines the impact of port failures on the host urban enviroment and the relationship between hazards, vulnerability and the impact. The vulnerability of the port to disasters results  to the vulnerability of its host city. A context –based understanding  of the impact of the disaster and the elements at risk is essential to identify appropriate risk management strategies. The location of the port within the urban environment, in densely populated area, as in case of Beirut are some of the characteristics of the port cities that can magnify the impact of disasters to which they are prone.  The study will focus on a collection of data that records the impact and allows visualisation of the complex patterns of the disaster risk reduction.</p><p>The impact caused by the Beirut’s port explosion reminds us about the important role of the ports in their host cities and how fundamental is to identify the port’s infrastructure  exposure to hazards and risks.  Lessons learned from such event may be useful to reduce disaster risks in the port cities.</p>

scholarly journals Impact of precipitation intermittency on NAO-temperature signals in proxy records

2013 ◽  
Vol 9 (2) ◽  
pp. 871-886 ◽  
Author(s):  
M. Casado ◽  
P. Ortega ◽  
V. Masson-Delmotte ◽  
C. Risi ◽  
D. Swingedouw ◽  
...  
Keyword(s):  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ice Cores ◽  
Stable Isotope Ratio ◽  
Global Network ◽  
Temporal Correlations ◽  
The North ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract. In mid and high latitudes, the stable isotope ratio in precipitation is driven by changes in temperature, which control atmospheric distillation. This relationship forms the basis for many continental paleoclimatic reconstructions using direct (e.g. ice cores) or indirect (e.g. tree ring cellulose, speleothem calcite) archives of past precipitation. However, the archiving process is inherently biased by intermittency of precipitation. Here, we use two sets of atmospheric reanalyses (NCEP (National Centers for Environmental Prediction) and ERA-interim) to quantify this precipitation intermittency bias, by comparing seasonal (winter and summer) temperatures estimated with and without precipitation weighting. We show that this bias reaches up to 10 °C and has large interannual variability. We then assess the impact of precipitation intermittency on the strength and stability of temporal correlations between seasonal temperatures and the North Atlantic Oscillation (NAO). Precipitation weighting reduces the correlation between winter NAO and temperature in some areas (e.g. Québec, South-East USA, East Greenland, East Siberia, Mediterranean sector) but does not alter the main patterns of correlation. The correlations between NAO, δ18O in precipitation, temperature and precipitation weighted temperature are investigated using outputs of an atmospheric general circulation model enabled with stable isotopes and nudged using reanalyses (LMDZiso (Laboratoire de Météorologie Dynamique Zoom)). In winter, LMDZiso shows similar correlation values between the NAO and both the precipitation weighted temperature and δ18O in precipitation, thus suggesting limited impacts of moisture origin. Correlations of comparable magnitude are obtained for the available observational evidence (GNIP (Global Network of Isotopes in Precipitation) and Greenland ice core data). Our findings support the use of archives of past δ18O for NAO reconstructions.

Response Analysis of van der Pol Vibro-Impact System with Coulomb Friction Under Gaussian White Noise

2018 ◽  
Vol 28 (13) ◽  
pp. 1830043 ◽  
Author(s):  
Meng Su ◽  
Wei Xu ◽  
Guidong Yang
Keyword(s):  
White Noise ◽  
Coulomb Friction ◽  
Gaussian White Noise ◽  
Original System ◽  
Stochastic Averaging ◽  
Response Analysis ◽  
State Variables ◽  
Van Der Pol ◽  
Impact System ◽  
The Impact

In this paper, the stationary response of a van der Pol vibro-impact system with Coulomb friction excited by Gaussian white noise is studied. The Zhuravlev nonsmooth transformation of the state variables is utilized to transform the original system to a new system without the impact term. Then, the stochastic averaging method is applied to the equivalent system to obtain the stationary probability density functions (pdfs). The accuracy of the analytical results obtained from the proposed procedure is verified by those from the Monte Carlo simulation based on the original system. Effects of different damping coefficients, restitution coefficients, amplitudes of friction and noise intensities on the response are discussed. Additionally, stochastic P-bifurcations are explored.

scholarly journals Atmospheric Mercury Concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network

2016 ◽  
Author(s):  
Francesca Sprovieri ◽  
Nicola Pirrone ◽  
Mariantonia Bencardino ◽  
Francesco D’Amore ◽  
Francesco Carbone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Ad Hoc ◽  
Temporal Trends ◽  
Global Scale ◽  
Atmospheric Mercury ◽  
Global Network ◽  
Observation System ◽  
Large Network ◽  
Deposition Processes ◽  
The Impact

Abstract. Long-term monitoring data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (www.gmos.eu), and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad-hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere, as well as in the lower stratosphere. To date more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010–2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern Hemisphere, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.

scholarly journals Cooperative UAV Scheme for Enhancing Video Transmission and Global Network Energy Efficiency

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4155 ◽  
Author(s):  
Pedro Cumino ◽  
Wellington Lobato Junior ◽  
Thais Tavares ◽  
Hugo Santos ◽  
Denis Rosário ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Video Transmission ◽  
State Of The Art ◽  
Premature Death ◽  
Global Network ◽  
Quality Level ◽  
Network Partitioning ◽  
Long Period ◽  
The Impact

Collaboration between multiple Unmanned Aerial Vehicles (UAVs) to set up a Flying Ad Hoc Network (FANET) is a growing trend since future applications claim for more autonomous and rapid deployable systems. The user experience on watching videos transmitted over FANETs should always be satisfactory even under influence of topology changes caused by the energy consumption of UAVs. In addition, the FANET must keep the UAVs cooperating as much as possible during a mission. However, one of the main challenges in FANET is how to mitigate the impact of limited energy resources of UAVs on the FANET operation in order to monitor the environment for a long period of time. In this sense, UAV replacement is required in order to avoid the premature death of nodes, network disconnections, route failures, void areas, and low-quality video transmissions. In addition, decision-making must take into account energy consumption associated with UAV movements, since they are generally quite energy-intensive. This article proposes a cooperative UAV scheme for enhancing video transmission and global energy efficiency called VOEI. The main goal of VOEI is to maintain the video with QoE support while supporting the nodes with a good connectivity quality level and flying for a long period of time. Based on an Software Defined Network (SDN) paradigm, the VOEI assumes the existence of a centrailized controller node to compute reliable and energy-efficiency routes, as well as detects the appropriate moment for UAV replacement by considering global FANET context information to provide energy-efficiency operations. Based on simulation results, we conclude that VOEI can effectively mitigate the energy challenges of FANET, since it provides energy-efficiency operations, avoiding network death, route failure, and void area, as well as network partitioning compared to state-of-the-art algorithm. In addition, VOEI delivers videos with suitable Quality of Experience (QoE) to end-users at any time, which is not achieved by the state-of-the-art algorithm.

scholarly journals Dynamics of language reorganization after left temporo-parietal and frontal stroke

Brain ◽  
2020 ◽  
Vol 143 (3) ◽  
pp. 844-861 ◽  
Author(s):  
Anika Stockert ◽  
Max Wawrzyniak ◽  
Julian Klingbeil ◽  
Katrin Wrede ◽  
Dorothee Kümmerer ◽  
...  
Keyword(s):  
Functional Mri ◽  
Chronic Phase ◽  
Global Network ◽  
Lesion Location ◽  
Post Stroke ◽  
Language Functions ◽  
Language Recovery ◽  
Patient Groups ◽  
The Impact ◽  
General Networks

Abstract The loss and recovery of language functions are still incompletely understood. This longitudinal functional MRI study investigated the neural mechanisms underlying language recovery in patients with post-stroke aphasia putting particular emphasis on the impact of lesion site. To identify patterns of language-related activation, an auditory functional MRI sentence comprehension paradigm was administered to patients with circumscribed lesions of either left frontal (n = 17) or temporo-parietal (n = 17) cortex. Patients were examined repeatedly during the acute (≤1 week, t1), subacute (1–2 weeks, t2) and chronic phase (>6 months, t3) post-stroke; healthy age-matched control subjects (n = 17) were tested once. The separation into two patient groups with circumscribed lesions allowed for a direct comparison of the contributions of distinct lesion-dependent network components to language reorganization between both groups. We hypothesized that activation of left hemisphere spared and perilesional cortex as well as lesion-homologue cortex in the right hemisphere varies between patient groups and across time. In addition, we expected that domain-general networks serving cognitive control independently contribute to language recovery. First, we found a global network disturbance in the acute phase that is characterized by reduced functional MRI language activation including areas distant to the lesion (i.e. diaschisis) and subsequent subacute network reactivation (i.e. resolution of diaschisis). These phenomena were driven by temporo-parietal lesions. Second, we identified a lesion-independent sequential activation pattern with increased activity of perilesional cortex and bilateral domain-general networks in the subacute phase followed by reorganization of left temporal language areas in the chronic phase. Third, we observed involvement of lesion-homologue cortex only in patients with frontal but not temporo-parietal lesions. Fourth, irrespective of lesion location, language reorganization predominantly occurred in pre-existing networks showing comparable activation in healthy controls. Finally, we detected different relationships of performance and activation in language and domain-general networks demonstrating the functional relevance for language recovery. Our findings highlight that the dynamics of language reorganization clearly depend on lesion location and hence open new perspectives for neurobiologically motivated strategies of language rehabilitation, such as individually-tailored targeted application of neuro-stimulation.

e-Supply Network

2011 ◽  
pp. 250-268
Author(s):  
Shima Mohebbi ◽  
Rasoul Shafaei ◽  
Namjae Cho
Keyword(s):  
Capacity Utilization ◽  
Coordination Mechanism ◽  
Global Network ◽  
Supply Network ◽  
Agent Based ◽  
Network Cost ◽  
Network Coordination ◽  
Supply Capacity ◽  
The Impact ◽  
Total Network

The automation of negotiation among buyer-supplier-supplier triad is an important policy in e-supply network coordination (e-SNC). In addition to the buyer-supplier coordination advantages, a further coordination among suppliers is also highly important in order to maximize the network supply capacity utilization especially when the suppliers are geographically decentralized. This chapter focuses on the impact of suppliers’ coordination in a network where the coordination among buyers and suppliers is in place. The proposed agent-based model is composed of two negotiator agents, one monitor agent, and one coordinator agent. The model begins with buyer-supplier negotiation and coordination mechanism adopted from the approach developed by Mohebbi and Shafaei (2010). Then, the suppliers’ coordination mechanism is developed to investigate the interaction among suppliers and evaluate the subsequent benefit obtained in the global network. The efficiency of the proposed approach is evaluated using a simulation model. The results demonstrate that in a network where the coordination among buyers and suppliers is in place, a further coordination among suppliers leads to the reduction of total network cost.

scholarly journals Pattern Formation during the Impact of a Partially Frozen Binary Droplet on a Cold Surface

2020 ◽  
Vol 125 (18) ◽  
Author(s):  
Pallav Kant ◽  
Henrik Müller-Groeling ◽  
Detlef Lohse
Keyword(s):  
Pattern Formation ◽  
Cold Surface ◽  
The Impact

scholarly journals ‘A Nut We Have Officially yet to Crack’: Forcing the Attention of Athletic Departments Toward Sustainability Through Shared Governance

2019 ◽  
Vol 11 (19) ◽  
pp. 5198
Author(s):  
Martin Barrett ◽  
Kyle S. Bunds ◽  
Jonathan M. Casper ◽  
Michael B. Edwards ◽  
D. Scott Showalter ◽  
...  
Keyword(s):  
Sustainable Development ◽  
Intercollegiate Athletics ◽  
The United States ◽  
Coupled Systems ◽  
Structured Interviews ◽  
Athletic Departments ◽  
The Sustainable Development ◽  
Sustainability Governance ◽  
The Impact ◽  
Office Personnel

In many ways, intercollegiate athletics represents the ‘sustainable’ front porch of higher education. The high-visibility, high-impact nature of elite-level college athletics make athletic departments a central player in the sustainable development journey. However, not all athletic departments respond to this responsibility, nor are all responses uniformly successful. According to national reporting frameworks, an increasing number of universities in the United States are choosing to involve their athletic departments in university-level sustainability governance structures, but the benefits and limitations of this remain unclear. Using the theory of loosely coupled systems, and more specifically, the voice of compensations (which views loose coupling as an unsatisfactory state), the purpose of this paper is to explore perceptions of athletic department engagement in shared sustainability governance, and, thus, a whole-of-institution approach. Semi-structured interviews with sustainability office personnel were conducted and analyzed, and the findings imply that shared sustainability governance has the potential to focus the attention of athletic departments toward sustainability, as well as to reaffirm shared values. Yet, to maximize the impact of athletic departments toward the sustainable development goals of a university, sustainability office personnel suggest the deployment of additional change levers, in a multi-dimensional fashion, as supplementary coupling mechanisms. These would include more rigorous sustainability goals (top-down), continued collaboration on ‘low-hanging fruit’ initiatives (lateral), student-athlete engagement (bottom-up), and the development of an internal sustainability framework (inside-out).

scholarly journals Analyzing and interpreting neural networks for NLP: A report on the first BlackboxNLP workshop

2019 ◽  
Vol 25 (4) ◽  
pp. 543-557 ◽  
Author(s):  
Afra Alishahi ◽  
Grzegorz Chrupała ◽  
Tal Linzen
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Natural Language Processing ◽  
Language Processing ◽  
Performance Testing ◽  
Network Architectures ◽  
Empirical Methods ◽  
Neural Models ◽  
The Impact ◽  
Systematic Manipulation

AbstractThe Empirical Methods in Natural Language Processing (EMNLP) 2018 workshop BlackboxNLP was dedicated to resources and techniques specifically developed for analyzing and understanding the inner-workings and representations acquired by neural models of language. Approaches included: systematic manipulation of input to neural networks and investigating the impact on their performance, testing whether interpretable knowledge can be decoded from intermediate representations acquired by neural networks, proposing modifications to neural network architectures to make their knowledge state or generated output more explainable, and examining the performance of networks on simplified or formal languages. Here we review a number of representative studies in each category.

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