Simulation tools for multilayer fault restoration

BackgroundNew mathematical models of complex biological structures and computer simulation software allow modelers to simulate and analyze biochemical systems in silico and form mathematical predictions. Due to this potential predictive ability, the use of these models and software has the possibility to compliment laboratory investigations and help refine, or even develop, new hypotheses. However, the existing mathematical modeling techniques and simulation tools are often difficult to use by laboratory biologists without training in high-level mathematics, limiting their use to trained modelers.ResultsWe have developed a Boolean network-based simulation and analysis software tool, ChemChains, which combines the advantages of the parameter-free nature of logical models while providing the ability for users to interact with their models in a continuous manner, similar to the way laboratory biologists interact with laboratory data. ChemChains allows users to simulate models in an automatic fashion under tens of thousands of different external environments, as well as perform various mutational studies.ConclusionChemChains combines the advantages of logical and continuous modeling and provides a way for laboratory biologists to perform in silico experiments on mathematical models easily, a necessary component of laboratory research in the systems biology era.

This paper examines three distinct methods of designing an ATM core network which is resilient to any single cable break (often the most common type of major failure): (1) The ATM crossconnects are collocated with SDH 4/4 crossconnects, and VPs are multiplexed onto VC-4s which are routed through the SDH crossconnect platform. Protection is at the SDH layer, with backup VC-4 routes assigned to working VC-4s. (2) As in option 1, ATM crossconnects are collocated with SDH crossconnects, and VPs are multiplexed onto VC-4s which are routed through the SDH crossconnect platform. The protection in this case is at the ATM layer, with backup VPs assigned to working VPs. (3) ATM crossconnects are collocated at SDH crossconnect sites, however the SDH crossconnects are not used for routing ATM traffic and point-to-point links transport the (single hop) VC-4s directly between ATM switches where VPs are multiplexed/demultiplexed. Protection is at the ATM layer, with backup VPs assigned to working VPs. The principal goal is to evaluate the schemes in terms of the cost required to provide resilience to ATM traffic from any single cable break.

A magnetic induction based underwater communication link is evaluated using an analytical model and a custom Finite-Difference Time-Domain (FDTD) simulation tool. The analytical model is based on the Sommerfeld integral, and a full-wave simulation tool evaluates Maxwell's equations using the FDTD method in cylindrical coordinates. The analytical model and FDTD simulation tool are then compared and used to predict the system performance for various transmitter depths and optimum frequencies of operation. To this end, the system bandwidth, signal to noise ratio, and the magnitude of the induced voltage are used to estimate the expected channel capacity. The models show that in seawater, a relatively low-power and small coil may be capable of obtaining a throughput of 40 to 300 kbps, for the case where a transmitter is at depths of 1 to 3 m and a receiver is at a height of 1 m.

NASA is planning to upgrade its network infrastructure to support missions for the 21st century. The first step is to increase the data rate provided to science missions to at least the 100 Mbps range. This is under way, using Ka-band 26 GHz, erecting an 18-meter antenna for the Lunar Reconnaissance Orbiter, and the planned upgrade of the Deep Space Network (DSN) 34-meter network to support the James Webb Space Telescope (JWST). The next step is the support of manned missions to the Moon and beyond. Establishing an outpost with several activities such as rovers, colonization, and observatories, is better achieved by using a network configuration rather than the current method of point-to-point. Another challenge associated with the Moon is communication coverage with the Earth. The Moon's South Pole, targeted for human habitat and exploration, is obscured from Earth view for half of the 28-day lunar cycle and requires the use of lunar relay satellites to provide coverage for the times when there is no direct view of the Earth. The future NASA and Constellation network architecture is described in the Space Communications Architecture Working Group (SCAWG) Report[l]. The Space Communications and Navigation (SCAN) Constellation Integration Project (SCIP) is responsible for coordinating Constellation requirements and has assigned the responsibility for implementing these requirements to the existing NASA communication providers: DSN, Space Network (SN), Ground Network (GN) and the NASA Integrated Services Network (NISN). The SCAWG Report provides a future architecture but does not provide implementation details. The architecture calls for a Netcentric system, using hundreds of 12-meter antennas, a ground antenna array, and a relay network around the Moon. The report did not use cost as a variable in determining the feasibility of this approach. As part of the SCIP Mission Concept Review and the second iteration of the Lunar Architecture Team (LAT), the focus is on cost, as well as communication coverage using operational scenarios. This approach maximizes use of existing assets and adds capability in small increments. This paper addresses architecture decisions such as the Radio Frequency (RF) signal and network (Netcentric) decisions that need to be made and the difficulty of implementing them into the existing Space Network and DSN. It discusses the evolution of the lunar system and describes its components: TDRSS, Earth-based ground stations, Lunar Relay, and surface systems.

A study conducted to better understand the impact of declining transmission costs on the design of future fiber-based telecommunications network architectures is described. The study consists of quantifying the costs of switches, trunk and loop plant, building, and outside plant enclosures in order to determine the most economical number of switching nodes in the study areas based on the current equipment and land/building prices as well as the expected prices in the 1995 time frame. The results of this study show that the network architectures with fewer but larger switching nodes accompanied by back hauling of traffic via fiber optics and large multiplexers/concentrators offer significant savings potential in rural/suburban areas and low-to-moderate savings in urban areas as compared to architectures with many smaller switching nodes. In a broadband network environment, the results are shown to be valid for small penetrations of broadband services (less than 10%) and small broadband call bandwidths (equal to or less than 45 Mb/s). >

Scaling traditional telecommunication networks so that they are able to cope with the volume of future traffic demands and the stringent European Commission (EC) regulations on emissions would entail unaffordable investments. For this very reason, the design of an innovative ultra-high bandwidth power-efficient network architecture is nowadays a bold topic within the research community. So far, the independent evolution of network layers has resulted in isolated, and hence, far-from-optimal contributions, which have eventually led to the issues today's networks are facing such as inefficient energy strategy, limited network scalability and flexibility, reduced network manageability and increased overall network and customer services costs. Consequently, there is currently large consensus among network operators and the research community that cross-layer interaction and coordination is fundamental for the proper architectural design of next-generation Internet networks. This thesis actively contributes to the this goal by addressing the modeling, optimization and performance analysis of a set of potential technologies to be deployed in future cross-layer network architectures. By applying a transversal design approach (i.e., joint consideration of several network layers), we aim for achieving the maximization of the integration of the different network layers involved in each specific problem. To this end, Part I provides a comprehensive evaluation of optical transport networks (OTNs) based on layer 2 (L2) sub-wavelength switching (SWS) technologies, also taking into consideration the impact of physical layer impairments (PLIs) (L0 phenomena). Indeed, the recent and relevant advances in optical technologies have dramatically increased the impact that PLIs have on the optical signal quality, particularly in the context of SWS networks. Then, in Part II of the thesis, we present a set of case studies where it is shown that the application of operations research (OR) methodologies in the desing/planning stage of future cross-layer Internet network architectures leads to the successful joint optimization of key network performance indicators (KPIs) such as cost (i.e., CAPEX/OPEX), resources usage and energy consumption. OR can definitely play an important role by allowing network designers/architects to obtain good near-optimal solutions to real-sized problems within practical running times.

Named data networking (NDN) has emerged as a future networking architecture having the potential to replace the Internet. In order to do so, the NDN needs to cope with inherent problems of the Internet, such as attacks that cause information leakage from an enterprise. Since NDN has not yet been deployed on a large scale, it is currently unknown how such attacks can occur, let alone what countermeasures can be taken against them. In this paper, we first show that information leakage in NDN can be caused by malware inside an enterprise, which uses steganography to produce malicious interest names encoding confidential information. We investigate such attacks by utilizing a content name dataset based on uniform resource locators (URLs) collected by a Web crawler. Our main contribution is a name filter based on anomaly detection that takes the dataset as input and classifies a name in the Interest as legitimate or not. Our evaluation shows that the malware can exploit the path part in the URL-based NDN name to create malicious names, thus, information leakage in the NDN cannot be prevented completely. However, we show for the first time that our filter can dramatically choke the leakage throughput causing the malware to be 137 times less efficient at leaking information. This finding opens up an interesting avenue of research that could result in a safer future networking architecture.

A comprehensive review on biosorption of heavy metals by algal biomass: Materials, performances, chemistry, and modeling simulation tools

To analyze controller area network protocol and evaluate CAN network performance, this paper provides a way in which the Layered modeling method is adopted to build the CAN network model in the OPNET Modeler simulation environment. The models of Logical Link Control and Medium Access Control of CAN protocol with the functions of error handling and channel status detection were established in the OPNET node Layer; and the model of CAN bus physical layer was designed to implement collision detection and nondestructive arbitration functionality in the OPNET Pipeline Stages. A case model was simulated in a specifically network environment, through analyze the simulation result, a research was made into the CAN bus performance such as End-to-End delay and throughput. These results show that the OPNET model can effectively describe and analyze the communication behavior of CAN bus, and set up a good basis for further design and realization of communication protocols.

Managing uncertainty in integrated environmental modelling: The UncertWeb framework

Fracture toughness parameter is significantly affected by specimen dimensions i.e. specimen thickness (B), width (W) and unbroken ligament length (W-ao) in elastic-plastic region. Present study is about the third dimension of test specimen (W-ao). In order to investigate effect of ao/W ratio on fracture toughness parameter, fracture test and finite-element - cohesive zone model (CZM) simulation tool are used. Fracture tests are carried out on extra deep drawn (EDD) steel sheets using compact tension (CT) type specimens with different ao/W ratio (0.5, 0.525, 0.55 and 0.575). After successive experimental attempts, load drop technique is used as a fracture criterion. Critical CTOD is used as a fracture toughness parameter. An alternative constant traction separation law is used to account for maximum load and large load line displacements. Experimental findings as well as finite element studies show that the critical CTOD decreases with ao/W ratio. It has been observed that as ao/W ratio increases, the location of plastic hinge shifts towards the crack tip (i.e. size of tensile plastic zone reduces), which reduces fracture toughness. That is, the material is less resistant to crack growth for deeper cracks.

EOOLT 2010 was the third edition of the EOOLT workshop series. The workshop is intended to bring together researchers and practitioners from-different equation-based object-oriented (EOO) modeling language communities. This year's workshop also expands the scope to include the whole design space of languages for cyber-physical systems, where physical dynamics are mixed with networks and software. The workshop gathered 31 participants to present and discuss thirteen different papers grouped into the four areas of realtime oriented modeling languages and tools, modeling language design, simulation and model compilation, and modeling and simulation tools.

It is an undeniable fact that software plays an important role in our lives. We use the software to play our music, to check our e-mail, or even to help us drive our car. Thus, the quality of software directly influences the quality of our lives. However, the traditional Software Engineering paradigm is not able to cope with the increasing demands in quantity and quality of produced software. Thus, a new paradigm of Model Driven Software Engineering (MDSE) is quickly gaining ground. MDSE promises to solve some of the problems of traditional Software Engineering (SE) by raising the level of abstraction. Thus, MDSE proposes the use of models and model transformations, instead of textual program files used in traditional SE, as means of producing software. The models are usually graph-based, and are built by using graphical notations – i.e. the models are represented diagrammatically. The advantages of using graphical models over text files are numerous, for example it is usually easier to deduce the relations between different model elements in their diagrammatic form, thus reducing the possibility of defects during the production of the software. Furthermore, formal model transformations can be used to produce different kinds of artifacts from models in all stages of software production. For example, artifacts that can be used as input for model checkers or simulation tools can be produced. This enables the checking or simulation of software products in the early phases of development, which further reduces the probability of defects in the final software product. However, methods and techniques to support MDSE are still not mature enough. In particular methods and techniques for model configuration management (MCM) are still in development, and no generic MCM system exists. In this thesis, I describe my research which was focused on developing methods and techniques to support generic model configuration management. In particular, during my research, I focused on developing methods and techniques for supporting model evolution and model co-evolution. Described methods and techniques are generic and are suitable for a state-based approach to model configuration management. In order to support the model evolution, I developed methods for the representation, calculation, and visualization of state-based model differences. Unlike in previously published research, where these three aspects of model differences are dealt with in separation, in my research all these three aspects are integrated. Thus, the result of model differences calculation algorithm is in the format which is described by my research on model differences representation. The same representation format of model differences is used as a basis of my approach to differences visualization. It is important to notice that the developed representation format for model differences is metamodel independent, and thus is generic, i.e., it can be used to represent differences between all graph-based models. Model co-evolution is a term that describes the problem of adapting models when their metamodels evolve. My solution to this problem has three steps. In the first step a special metamodel MMfMM is introduced. Unlike in traditional approaches, where metamodels are represented as instances of a metametamodel, in my approach the metamodels are represented by models which are instances of an MMfMM. In the second step, since metamodels are represented by models, previously defined methods and techniques for model evolution are reused to represent and calculate the metamodel differences. In the final step I define an algorithm that uses the calculated metamodel differences to adapt models conforming to the evolved metamodel. In order to validate my approaches to model evolution and model co-evolution, I have developed a tool for comparing models and visualizing resulting differences, and a tool for model co-evolution. Moreover, I have developed a method to compare tools for model comparison, and using this method I have conducted a series of experiments in which I compared the tool I developed to an industrial tool called EMFCompare. The results of these experiments are also presented in the thesis. Furthermore, in order to validate my tool and approach to model co-evolution, I have also specified and conducted several experiments. The results of these experiments are also presented in the thesis.

Business process analysts prefer to build business process models (BPM) using graphical languages like BPMN or UML Activity Diagrams. Several researchers have presented validation methologies for such BPMs. In order to use these verification techniques for BPMs written in graphical languages, the models must be translated into the input language of a model checker or simulation tool. By analyzing 285 BPMs (modelled as Event driven Process Chains (EPC)), we found that checking restrictions for ”good modeling style” before starting the translation process has three positive effects: It can make the translation algorithm much easier, can improve the quality of the BPM by substituting ”bad constructs” automatically and can help to identify erroneous models.

Abstract. In recent years, the threat of cyberattacks has been growing rapidly in numerous industrial sectors that have an impact on our daily life. One of these is the space industry, where the risk of hacking a single satellite can lead to dangerous effects not only for economics but also for Earth critical infrastructure like: transportation systems, water networks, and electric grid. The vulnerability of complex space systems has already been demonstrated in the past. In 1998, for example, hackers took control of the ROSAT X-Ray satellite pointing its solar panels directly to the Sun and causing physical damage. Nowadays, since the attention is moved on small and less sophisticated system, such as CubeSat, the risk of cyber intrusions is even higher as the COTS (Commercial-Off-The-Shelf) technology they use is based on open-source operating systems. In order to counteract this imminent problem, the development of a high-fidelity CubeSat digital model is needed to study and solve related space cybersecurity issues. In fact, thanks to the virtual prototype, what-if simulations can be performed allowing to analyze different cyberattacks scenarios and predict undesirable events on the CubeSat flying on its operative orbit. Moreover, the building of the digital model requires a holistic modeling approach and simulation tools which allows to consider Multiphysics phenomena occurring on the space system itself. Finally, the possibility of connecting the virtual model to a real space system, obtaining the so-called Digital Twin (DT), will help engineers to conduct more accurate actions during the mission.