scholarly journals Evaluation of Network Reliability for Computer Networks with Multiple Sources

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Yi-Kuei Lin ◽  
Louis Cheng-Lu Yeng
Keyword(s):  
New York ◽  
Computer Networks ◽  
Land Surface ◽  
Computer Network ◽  
Network Reliability ◽  
Network Models ◽  
Critical Issue ◽  
The United States ◽  
Service Level ◽  
Multiple Sources

Evaluating the reliability of a network with multiple sources to multiple sinks is a critical issue from the perspective of quality management. Due to the unrealistic definition of paths of network models in previous literature, existing models are not appropriate for real-world computer networks such as the Taiwan Advanced Research and Education Network (TWAREN). This paper proposes a modified stochastic-flow network model to evaluate the network reliability of a practical computer network with multiple sources where data is transmitted through several light paths (LPs). Network reliability is defined as being the probability of delivering a specified amount of data from the sources to the sink. It is taken as a performance index to measure the service level of TWAREN. This paper studies the network reliability of the international portion of TWAREN from two sources (Taipei and Hsinchu) to one sink (New York) that goes through a submarine and land surface cable between Taiwan and the United States.

scholarly journals Modeling the dynamics of COVID19 spread during and after social distancing: interpreting prolonged infection plateaus

2020 ◽  
Author(s):  
Natalia L. Komarova ◽  
Dominik Wodarz
Keyword(s):  
New York ◽  
Network Models ◽  
The United States ◽  
Social Distancing ◽  
Decline Phase ◽  
Intervention Measures ◽  
Infection Dynamics ◽  
Infection Models ◽  
Second Wave ◽  
Infection Spread

AbstractNon-pharmaceutical intervention measures, such as social distancing, have so far been the only means to slow the spread of COVID19. In the United States, strict social distancing has resulted in different types infection dynamics. In some states, such as New York, extensive infection spread was followed by a pronounced decline of infection levels. In other states, such as California, less infection spread occurred before strict social distancing, and a different pattern was observed. Instead of a pronounced infection decline, a long-lasting plateau is evident, characterized by similar daily new infection levels. While these plateau dynamics cannot be readily reproduced with standard SIR infection models, we show that network models, in which individuals and their social contacts are explicitly tracked, can reproduce the plateau if network connections are cut due to social distancing measures. The reason is that in networks characterized by a 2D spatial structure, infection tends to spread quadratically with time, but as edges are randomly removed, the infection spreads along nearly one-dimensional infection “corridors”, resulting in plateau dynamics. Interestingly, the plateau dynamics are predicted to eventually transition into an infection decline phase without any further increase in social distancing measures. Additionally, the models suggest that a potential second wave becomes significantly less pronounced if social distancing is only relaxed once the dynamics have transitioned to the decline phase. The network models analyzed here allow us to interpret and reconcile different infection dynamics during social distancing observed in various US states.

scholarly journals Model of Threats to Computer Network Software

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1506 ◽  
Author(s):  
Aleksey Novokhrestov ◽  
Anton Konev ◽  
Alexander Shelupanov
Keyword(s):  
Information Security ◽  
Computer Networks ◽  
Network Model ◽  
Computer Network ◽  
Network Models ◽  
Security Threats ◽  
Software Components ◽  
Mathematical Apparatus ◽  
Network Software

This article highlights the issue of identifying information security threats to computer networks. The aim of the study is to increase the number of identified threats. Firstly, it was carried out the analysis of computer network models used to identify threats, as well as in approaches to building computer network threat models. The shortcomings that need to be corrected are highlighted. On the basis of the mathematical apparatus of attributive metagraphs, a computer network model is developed that allows to describe the software components of computer networks and all possible connections between them. On the basis of elementary operations on metagraphs, a model of threats to the security of computer network software is developed, which allows compiling lists of threats to the integrity and confidentiality of computer network software. These lists include more threats in comparison with the considered analogues.

Optimal Component Quality Planning in Multi-State Computer Networks

2014 ◽  
Vol 31 (06) ◽  
pp. 1450049
Author(s):  
Shin-Guang Chen
Keyword(s):  
Computer Networks ◽  
Computer Network ◽  
Network Reliability ◽  
High Quality ◽  
Optimal Plan ◽  
Quality Planning ◽  
Business Operations ◽  
Novel Approach ◽  
The Cost ◽  
Component Quality

Computer networks are important infrastructures required by many modern corporations today. Maintaining a reliable computer network becomes an important issue in daily business operations. A computer network usually consists of components (including links or vertices) that may have several states due to failure, partial failure or maintenance, making it a multi-state computer network (MCN). This paper proposes a novel approach to create an optimal component quality plan in MCN. Finding the optimal component quality plan for an MCN requires searching for an optimal plan such that each component in the network has the proper level of quality while the network maintains highly reliable functionality. Because the costs of quality components are diversified, an appropriate plan for component quality distribution cannot only greatly reduce the cost of network installation but also maintain the network reliability. Another important consideration is that high-quality and expensive components may not increase network reliability if they are not placed appropriately. A novel heuristic approach is proposed to efficiently search for such plan. A comparison with the implicit enumeration method is conducted. The results show that the proposed approach is very effective and efficient. Some numerical examples are illustrated and explained in detail in this paper.

New Computer Network Paradigms and Virtual Organizations

2010 ◽  
pp. 1066-1073
Author(s):  
Guillermo Agustín Ibáñez Fernández
Keyword(s):  
Computer Networks ◽  
Packet Switching ◽  
Computer Network ◽  
The United States ◽  
Circuit Switching ◽  
Multiple Node ◽  
Small Set ◽  
Research Centres ◽  
Dominant Paradigm ◽  
Node Failures

A computer network consists of computers that communicate via any physical media through a network formed by links and nodes, the nodes being the computers. Computer networks have evolved along their short history. Computer networks have changed drastically in mission and implementation from the early projects supported by the Advanced Research Projects Agency (ARPA) and from other organizations, tracing back the origins to 1962. The ARPA network (ARPANET) consisted initially of a small set of nodes at research centres and universities, connected with links at 56 kbps across the United States. ARPANET was the core of the early Internet, a network for research centres and universities. Computer networks are based on the concept of packet switching within a shared communication medium, as opposite to circuit switching, the dominant paradigm for the precedent telegraph and telephone networks. In 1968 Paul Baran proposed a network system based on nodes that forward datagrams or packets from different users over a common line between computer systems from origin to destination. The packet switching paradigm provides resiliency of network against network node failures, the independent routing of datagrams per node makes possible that the datagrams reach their destination even in presence of multiple node failures.

New Computer Network Paradigms and Virtual Organizations

2010 ◽  
pp. 2343-2352
Author(s):  
Guillermo Agustín Ibáñez Fernández
Keyword(s):  
Computer Networks ◽  
Packet Switching ◽  
Computer Network ◽  
The United States ◽  
Circuit Switching ◽  
Multiple Node ◽  
Small Set ◽  
Research Centres ◽  
Dominant Paradigm ◽  
Node Failures

A computer network consists of computers that communicate via any physical media through a network formed by links and nodes, the nodes being the computers. Computer networks have evolved along their short history. Computer networks have changed drastically in mission and implementation from the early projects supported by the Advanced Research Projects Agency (ARPA) and from other organizations, tracing back the origins to 1962. The ARPA network (ARPANET) consisted initially of a small set of nodes at research centres and universities, connected with links at 56 kbps across the United States. ARPANET was the core of the early Internet, a network for research centres and universities. Computer networks are based on the concept of packet switching within a shared communication medium, as opposite to circuit switching, the dominant paradigm for the precedent telegraph and telephone networks. In 1968 Paul Baran proposed a network system based on nodes that forward datagrams or packets from different users over a common line between computer systems from origin to destination. The packet switching paradigm provides resiliency of network against network node failures, the independent routing of datagrams per node makes possible that the datagrams reach their destination even in presence of multiple node failures.

scholarly journals The North American Soil Moisture Database: Development and Applications

2016 ◽  
Vol 97 (8) ◽  
pp. 1441-1459 ◽  
Author(s):  
Steven M. Quiring ◽  
Trent W. Ford ◽  
Jessica K. Wang ◽  
Angela Khong ◽  
Elizabeth Harris ◽  
...  
Keyword(s):  
Soil Moisture ◽  
North American ◽  
Land Surface ◽  
The United States ◽  
Important Variable ◽  
Climate System ◽  
Drought Monitoring ◽  
Multiple Sources ◽  
The North

Abstract Soil moisture is an important variable in the climate system that integrates the combined influence of the atmosphere, land surface, and soil. Soil moisture is frequently used for drought monitoring and climate forecasting. However, in situ soil moisture observations are not systematically archived and there are relatively few national soil moisture networks. The lack of observed soil moisture data makes it difficult to characterize long-term soil moisture variability and trends. The North American Soil Moisture Database (NASMD) is a new high-quality observational soil moisture database. It includes over 1,800 monitoring stations in the United States, Canada, and Mexico, making it the largest collections of in situ soil moisture observations in North America. Data are collected from multiple sources, quality controlled, and integrated into an online database (soilmoisture.tamu.edu). Here we describe the development of the database, including quality control/quality assurance, standardization, and collection of metadata. The utility of the NASMD is demonstrated through an analysis of the inter- and intraannual variability of soil moisture from multiple networks. The NASMD is a useful tool for drought monitoring and forecasting, calibrating/validating satellites and land surface models, and documenting how soil moisture influences the climate system on seasonal to interannual time scales.

Gerald H. Thayer's ornithological work in St Vincent and the Grenadines, Lesser Antilles

2018 ◽  
Vol 45 (1) ◽  
pp. 21-39 ◽  
Author(s):  
James W. Wiley
Keyword(s):  
New York ◽  
New York City ◽  
West Indies ◽  
The United States ◽  
Lesser Antilles ◽  
American Museum ◽  
The West ◽  
Comparative Zoology ◽  
North And South America ◽  
North And South

Gerald Handerson Thayer (1883–1939) was an artist, writer and naturalist who worked in North and South America, Europe and the West Indies. In the Lesser Antilles, Thayer made substantial contributions to the knowledge and conservation of birds in St Vincent and the Grenadines. Thayer observed and collected birds throughout much of St Vincent and on many of the Grenadines from January 1924 through to December 1925. Although he produced a preliminary manuscript containing interesting distributional notes and which is an early record of the region's ornithology, Thayer never published the results of his work in the islands. Some 413 bird and bird egg specimens have survived from his work in St Vincent and the Grenadines and are now housed in the American Museum of Natural History (New York City) and the Museum of Comparative Zoology (Cambridge, Massachusetts). Four hundred and fifty eight specimens of birds and eggs collected by Gerald and his father, Abbott, from other countries are held in museums in the United States.

Sign in / Sign up

Export Citation Format

Share Document