Distributed Systems

Distributed Systems

  • Irina A. Lomazova added an answer:
    Are there any references regarding calculating concurrent transitions from an arbitrary Petri net?

    I mean an approach to find all concurrent transitions directly from a Petri net structure. 

    Irina A. Lomazova · National Research University Higher School of Economics

    The problem is decidable, it's the coverability problem. To check whether several transitions can fire simultaniously one needs to check, that a marking covering the sum of all presets for these transitions is reachable.

    Consult the paper http://www.sciencedirect.com/science/article/pii/0890540190900097

  • Peter T Breuer added an answer:
    Qualification of a Time and Space Partitioning (TSP) kernel: how formal methods could help ?

    I have an issue concerning the verification and validation of a TSP kernel... I would like to verify that for any configuration of the kernel, the kernel will satisfy the time and space segregation of the partitions. To be precise, I don't want to prove this property for all configurations but only configuration which respects the usage domain fixed by the kernel provider (bounds of the parameters or other structural constraints). The way to verify this is the following is to use unitary tests… To reduce the combination of tests, we have to make assumptions on the independence of (some, but more than less…) variables/configuration parameters. Using these assumptions we can drastically reduce the number of tests to be executed. Remain one thing: we have to prove or provide evidences that our assumptions are correct. To prove it, classical way is source code/ design inspection.

    My question is the following: how formal methods could help me at this stage? Can we prove independence between variables in a source code using formal methods and if yes, which method/technique?

    At first glance I see two ways to be explored:

    -          Either using formal static analysis to help the evaluator in the inspection of the source code and to prove independency of some variables… Have you any references of idea for helping doing that?

    -          Or trying to prove some invariants on an abstraction of the source code.  Does the independence of variables could be expressed as an invariant? How can I obtain a “good” abstraction of my source code to prove my invariant?  I hope that I can use source code annotation (something like ACSL annotation and Frama-C toolset) but I have not enough experience to see if it a reasonable or even feasible idea…. I can also hope that a magic static analysis tool could automatically generate an abstraction of the source code that I could use to prove my invariant using a theorem prover. But as for the previous one I have not enough experience to say if it is reasonable…

    Any idea and reference papers on the subject are welcome…

    Peter T Breuer · Birmingham City University

    I'm afraid that stuff is just not an explanation. It's terrible. It's description, not explanation. An explanation must start from where the reader is, not where the writer is, and inform the reader about the writer's unspoken assumptions.

    Principle #1 of technical writing is to not use a term until you have defined it. That principle is violated one gazillion times in the first two sentences: "A TSP kernel is a kind of hypervisor. It ensures time and space seggregation of partitions which compose the system."

    You can't say "hypervisor". You haven't defined it. You can't say "kernel" you haven't defined that either! The best I can assume is you meant to write 'A "TSP kernel" is the SOFTWARE that runs in a computer, providing facilities and services to other low level software. It consists of handlers for hardware and software interrupts and faults. In particular, A "TSP kernel" provides services to operating systems, simulating a particular native hardware's responses and behaviour, and/or swapping between such simulations as required.'

    You can't say "space". There is no "space" in a computer. I have no idea what you mean by it. It is not defined. You can't say "partition" - you haven't defined it. To say that partitions "compose" a system is untrue .. there is the "hypervisor" itself that is not part of the "partitions", so either you mean something by "compose" that is not normal, or you mean something by "system" that is not normal, and both need defining. And so on and on ...

    OK, I could apply the whip some more. I won't. I hope that snaps you out of this mode of writing into something more accessible. You need to think from the reader's point of view. People can help you here. You just need to reach out to them. In particular, no formal methods person will have the faintest idea about hypervisors and operating systems (well, I can think of only one person, but I'm not convinced his appreciation would be recognized as real by real operating systems people) ... they likely will not be able to program in C, only prolog, haskell, scheme, etc.

    So you have some reaching out to do if you want a result.

    I'm not going to struggle through that appalling guff up there, myself, but I GUESS that you are describing what I stated in my sentence in quotes two or three paras ago.

    Of particular interest to me would be whether my guess at what a "hypervisor" is is correct, and what on earth you mean by "space", which I have not ventured to take a stab at.

    A quick scan of your writing seems to show that by "space" you mean something like sets of interrupts, memory mappings (ports), and peripherals. The natural meaning of "memory" seems not to be there. Please be specific.

  • Danh-Tai Hoang asked a question:
    How can we measure the order parameter (degree of synchronization) for a system with bimodal distribution, according Kuramoto model?

    I am considering a synchronization system of oscillators with Kuramoto model. Under a certain condition (parameter), the phase distribution of the system can be bimodal with a different phase of \pi, and also can be multimodal under other condition. Order parameter as show in attachement is not consistent because R should be 0. Do you know how to measure the degree of synchronization for these cases? Thank you very much in advance.

  • Iwona Grobelna added an answer:
    What can i do to rectify the problem of hanging in TimeNet tool for Petri Net,anytime i want to simulate my model it always hang and have to close it?

    Anytime i want to perform token game or transient simulation or stationary simulation and generate graphs in result monitor it always hang, plss i need solution?

    Iwona Grobelna · University of Zielona Góra

    For tokengame, analysis or coverability graph generation of Petri Nets I use the WoPeD tool (http://woped.dhbw-karlsruhe.de/woped/). I works quite stable and so far I have no problems with it.

  • Arup Kumar Goswami asked a question:
    How can we decide the rating of DVR placed in a distribution system for voltage sag mitigation?

     What may be approximate cost of DVR?

  • Closed account added an answer:
    How can I validate the architecture for internet of things (IoT)?

    I am exploring some research ideas about architecture for IoT. At present I am come up to a naive idea for IoT architecture, but I am not clear about how to validate the naive architecture for IoT.

    Can anyone guide me in this regards, how to validate the architecture for IoT? what tool to be use? or any other guide line?

    Thanks in advance

    Deleted · Universidad Politécnica de Madrid

    There isn't really such a thing as THE Internet of things, what there is, is a large collect of different Internet of things. To reinforce the points made by Trudi Schifter, not only is there not one service level architecture, for example there is a massive difference between the operation requirements of a large scale sensor network and bunch of home based actuator and control systems. A sensor network requires massive levels of aggregation within in the carrier network and a home network requires a single secure gateway control point supporting typically full duplex communications. There is not even a single transport architecture. One way of looking at things such a as z-wave, or zigbee is to regard them as local area transport system. The picture is often confused because the underlying wireless network is nearly always associated very closely with its function. Again for example a home based heating control thermostat is defined by is function, not its gateway protocol. However, these gateway technologies are flexible transport systems and can be used to support a huge range of applications. Also a given technology is not always appropriate. Zigbee may be of no use to you if the devices are deployed over a wide area with large separation between device, or if the systems are to produce high bandwidth output.

    In addition to these underlying connectivity technologies being different, the developer base has different requirements. Some one who wants to use the output of a device, or control it, really is only interested in the code, or API, to do this. So they are only interested in the address of the device and how to talk to it. This is almost always via a gateway point, usually in the form of a web service. However the device designers are interested in the details of the device operation, circumnavigation firewalls and providing security. The hobbyist/end application developer will typically see things from the point of view of the gateway bridge, for example a z-wave gateway, or a zigbee bridge. So the different user groups see the architecture in different ways. Because of this I don't think there is ever going to be a one size fits all solution. The problem is the term Internet of things is too general a description, its OK for marketing purposes, but its not useful from a technical perspective.

    Now to answer your question. To validate an architecture is extremely difficult in general and because the ideas around this subject are in their infancy its an order of magnitude more complex. In my experience the only option is to build it and test it. Again as an example, we found on of the most annoying problems is managing the flow of data over private networks and through firewalls, which was not an obvious architectural problem when we stated deploying sensors.

  • Akinwale Akinwunmi added an answer:
    how can a programming language be selected for developing distributed systems?

    Programming languages and distributed systems have long influenced each other. Naturally, every programming language has its strengths and weaknesses. Consequently, it might be difficult to decide precisely which language should be chosen for a software project. However, the selection of the right programming language can be crucial to the success of a project or a software system.

    Akinwale Akinwunmi · Bowen University

    There are programming languages with capabilities for distributed computing such as java and python. The functionality required for such project will determine which way to go after proper scrutiny of the features of the supporting programming languages.

  • Suman Bhullar added an answer:
    In a load flow of radial distribution system can we generate complex power so that current will become minimum and hence maximum V1?

    I have to develop a load flow model of balanced radial distribution system. I want to apply optimization techniques, so that current becomes minimum and voltage at the receiving will become maximum.

    V2= V1- Ijj Zjj

    where V1= voltage at the sending end node and V2= voltage at the receiving end node;

    Ijj= branch current and Zjj= branch impedance;

    branch current further depends upon complex power and voltage which is assumed to be constant.

    By optimization technique can we generate complex power so that current will become minimum and hence maximum V1?

    What will be the objective function?

    F(x)= Min Ijj?

    Am i right?

    or F(x)= Max

    Suman Bhullar · Thapar University

     Thank u to all of u for sparing time for my query. it is very good platform for researchers to discuss their problems .

  • Persis Pratap added an answer:
    How can I create a Petri net simulator?

    Hello everyone,

    I would like to make a simulation of a particular Petri net.

    Is there someone that can help me with some ideas or principles on this?

    Thank you in advance!

    Persis Pratap · Madras Christian College

    Hi,

    The Petri net simulator can be made as a trial run using a free open source - WOPED. it has all built in properties of petri nets. just draw and connect your tokens in petri nets to find amazing results.

  • Petros Aristidou added an answer:
    Can anyone suggest an algorithm for the application of MPC in distribution system?

    Hi

    Can Anyone suggest an easy implemented  algorithm for the application of using Distributed Model Predictive Control for voltage control in Distribution system. A distribution system with Dgs, capacitor bank, storage units, AVR. And is there any way to transfer info between two control models each one controls a specific zone in the system.

    Thanking

    Petros Aristidou · University of Liège

    For more power system oriented applications, check out the following papers. There are many things in their references.

  • Allan E. S. Freitas added an answer:
    What are recent real time issues in distributed system security?

    I want to know the issues around distributed system security and how can be remoduled to give proposed possible things to overcome?

    Allan E. S. Freitas · Instituto Federal de Educação, Ciência e Tecnologia da Bahia (IFBA)

    You have to keep control on available resources, in order to keep the required constraints for the real-time distributed system.

  • Mostafa Eidiani added an answer:
    How can I performance a load scaling in PSSe?

    How can I performance a load scaling in PSSe?

    Mostafa Eidiani · Khorasan Institute of Higher Education

    Hi Dear Pierre and mingtian

    Thank you so much

  • Monsef Tahir added an answer:
    How can I use distributed model predictive control for Voltage Control?

    Hi

    I am looking to use MPC for voltage control in distribution systems with the existence of DGs and storage units. I am trying to use OpenDss to run power flow while using Matlab to build the control model. My question is, How can I transfer information between the two MPCs and send the control signals to openDss to change control parameters such as LTC, DG power factor,...so on?. Since the openDss solves either snapshot or hourly, Is there any better software to use for simplicity?

    Regards 

    Monsef Tahir · University of Waterloo

    Thank you very much Marinko.

    Actually you add a lot to what i am looking for. I hope you do not mind if i need more help.

    Regards

  • Mostafa Eidiani added an answer:
    Can we draw a simulink model of a radial distribution system?

    I haven't seen any paper containing simulink model of radial distribution system  except some software .e.g. ETAP.

    Mostafa Eidiani · Khorasan Institute of Higher Education

    You can see also this link

    http://www.uploadbaz.com/s5dewp9651st

  • Adelhard Rehiara added an answer:
    How can I get the full parameters of a 3ph induction motor using current and voltage measurements?

    I have an inverter and Siemens 3ph induction motor model 1LA7060-4AB10

    I want to measure or estimate the parameters of this motor such as :

    Rotor resistance

    Stator resistance

    Rotor leakage inductance

    Stator leakage inductance

    Mutual inductance

    Using the input voltage and the currents

    Adelhard Rehiara · State University of Papua

    Hi Gad. I think the paper from MAYANK PRATAP SINGH titled "Parameter Estimation of Three Phase Induction Motor:An Innovative Approach” can also be your reference. Find it in the link.

  • Happymore Mbiza added an answer:
    What are the effects of water storage and its impact on urban distribution system?

    There are severe water rationing practices that have resulted in consumers opting for storage than waiting for the next supply. This storage in turn has its effects on the water distribution system of a community.

    Happymore Mbiza · UNESCO-IHE Institute for Water Education

    Thank you all for the useful responses.

  • Stanislav Simeonov added an answer:
    Can someone please explain the difference between offline and online scheduling on multicore systems with examples?

    I have been working on task allocation policies and load balancing algorithms (Best Fit, Worst Fit, Next Fit, First Fit, etc). I have read some papers on online and offline scheduling techniques but I found it difficult to understand. I would be grateful if someone can explain the difference or cite a link to the same.

    Thanks in advance.

    Stanislav Simeonov · Bourgas "Prof. Assen Zlatarov" University

    Dear Anmol,

    A scheduler is offline if the scheduling decisions are made prior to the running of the system. A table is generated that contains the necessary scheduling decisions for use during the run-time.An online scheduler makes scheduling decisions during the run-time of the system. It can be either static or dynamic. The decisions are based on both process characteristics and the current state of the system.

  • Manish Tembhurkar added an answer:
    What is the technique, method, etc. I can use this to make a General Purpose Macro-Processor GPMP smarter?

    From the view of design, which smart technique, method, etc. can I use it for GPMP.

    Manish Tembhurkar · Raisoni Group of Institutions

    Hello Ayad,

    Try using this tool

    Gema (http://gema.sourceforge.net/new/index.shtml)

    I hope this will help you out with the issue.

    With Regards,

    Manish

  • Sudhanshu Singh added an answer:
    Is there anyone working in reconfiguration of radial distribution system?

    I want to know if all the reconfigured cases of a system (eg. IEEE 33 bus Radial system) gets convergence when we run load flow study, provided the reconfigured system is radial. Kindly anyone help me.

    Sudhanshu Singh · Indian Institute of Science

    Omnet++ is based on C++ so try the following:

    //msg is your normal string for sending message from tictoc example

    int k =10; //your number
    std::stringstream intMsg;
    intMsg << k;
    msg = intMsg.str();

    to read back you can use atoi function

    Hope it helps.

    Cheers

  • How can I calculate the gradient of initial state equations?

    If you have linear dynamical systems with infinite dimensional distributed systems. How can determine the initial gradient state if we have state equation with initial state and augmented by output function?

    Raheam A Mansor Al-Saphory · University of Tikrit

    Hernando Castaneda Marin

    Many thanks for your reply

    Regards

  • Ranajit Dey added an answer:
    How can I measure the nonsingularity of a matrix quantitatively?

        A nonsingular matrix maybe very close to a singular one, e.g. if the absolute values of elements in a row are all very small, then such a matrix is nearly singular.

        I can easily select a bunch of potential indices to quantitatively measure the nonsingularity of matrix, namely how far it is from being singular, e.g. the minimal modulus of eigenvalues or singular values, the absolute value of determinant...

        My  question is: Are there any documents which systematically discuss this issue, e.g. with comparisons between different indices?

        Thanks a lot!

    Ranajit Dey · Indian Space Research Organization, India, Ahmedabad

    General condition number is defined as norm(inv(A))*norm(A) where A is n/m matrix. For symmetric matrix this can be defined as max_eigenval/min_eigenval.

  • Sureshkumar Sudabattula added an answer:
    What is the base case power loss for 118 bus distribution system?

    i am working in distribution system side for comparing and analyse  my results according to my objective function. i am having some problem with 118 bus system because according to my load flow the base case power loss   i am getting is 1291kw but seeing so many papers it is 1296kw. than i have doubt which is correct?

    Sureshkumar Sudabattula · VIT University

    i am taking bus data and line data of 118 bus system and enter to my load flow and run the load flow getting base case power loss is 1291kw but compared some papers it is 1296kw which is correct?

  • H.F. Rashvand added an answer:
    What is directory indirection?

    I am reading a file system related paper. It says a concept "directory indirection". Can anyone explain to me how it works? And also, what is the difference and what are the benefits compared with the classical file system structure?

    H.F. Rashvand · Institute of Electrical and Electronics Engineers

    It can be counted as a security weakness, you may look at IEEE CS 2010 Paper from S. Kaxiras and G. Keramidas, also available for free download on:

    https://www.it.uu.se/katalog/steka984/05582068.pdf

  • Volker Lücken added an answer:
    Would FBMC for V2V applications be a good solution?

    FBMC also has a potential to cope better than OFDM with doubly dispersive
    channels when both the transmitting and receiving endpoints are moving (e.g., in a V2V application).

    Volker Lücken · RWTH Aachen University

    Ideally, when designing the filter, you should already be aware of the dispersive properties of the channel in both time and frequency dimension. This is why the Doppler spectrum needs to be predicted, e.g. by estimating the movement properties of the system.

  • Sivkumar Mishra asked a question:
    Can anyone provide the correct branch and load data of the 136 bus brazilian test distribution system?

    We require to test our reconfiguration algorithm on the 136 bus brazilian test distribution system. This radial test distribution system is used by many researchers for verifying the reconfiguration methods. In literature the results are available but not the correct line and load data including that of the tie lines.

  • Athanasios Anastasiou added an answer:
    Anyone familiar with Dial's algorithm(Dial 2006)?

    I need some help?

    I can't understand how to improve the bush when it isn't optimal.

    We should have a network where every arc has a mirror??

    if the arcs of the network don't have mirrors what we should do??

    In his article he said: "If the bush is not optimal, Algorithm B improves the bush by swapping out any of it's arcs having (non-bush) mirror with a negative reduced cost"

    Does that mean that the choice of the arc to swapp out  is random??

    Athanasios Anastasiou · Swansea University

    Hello

    Yes, every arc must have a mirror. If the mirror edge does not "exist" in the original graph just assign a very large weight to it, it will effectively never get selected.

    No, the selection of the arc is not at random. The added arc should lead to a lower min-path cost for the bush that is being examined.

    Hope this helps.

  • Syed Ali Raza Zaidi added an answer:
    Would network densification in future 5G help in reducing cost or other way round? How can the cost be reduced?

    Solving the capacity and data rate challenges with network densification could be very expensive in terms of equipment, maintenance, and operations in future 5G. In LTE and LTE-A most of the functionality of RAN and L2 layer was put on e-Node B. For 5G again it is being speculated to make simpler BS's. What would be the real solution to this?

    Syed Ali Raza Zaidi · University of Leeds

    Cloudification of radio access networks might solve issue to an extent. However, as Akram mentioned, pricing and business case remains an open ended problem from operator perspective.

  • Ugo Ghisla added an answer:
    Will LVDC systems be more efficient than actual existing LVAC systems? how, when & with which conditions ?

    It is common in most of existing Consumers to use a rectifier in order to convert AC to DC. Also dc power is more efficient specially in energy conversion systems used in distribution systems. If in a near future one can use DC instead of AC, It is now the proper time to have a look for a gradual change. So it needs planning . The question is when , How and with which expenses this replacement will occur?

    Ugo Ghisla · University of South Carolina

    Martin,

    I agree with you, changing international standard is not easy. However there can be workarounds: for example you could provide fault current limiting and extinction with static switches and once the fault current has extinguished utilize a mechanical contactor  as sectionalizer to exclude the faulted line and to introduce the required gap. This contactor will operate at zero current, so it wouldn't require the current capability of a circuit breaker, any cheap off-the-shelf contactor with sufficient rated voltage would serve the purpose.

  • James Ranjith Kumar R added an answer:
    Can we use forward-backward sweep method of load flow for radial systems with more than one source?

    When we use two or more sources buses in a radial distribution system, the power flows become bidirectional in some of the branches. In this case, can we use forward-backward sweep method for load flow study?

    James Ranjith Kumar R · Central Power Research Institute

    For generations having volage control can be modelled as PV buses. These PV buses can be handled along with the backward forward sweep algorithm using a sensitivity matrix method.

    One of the paper which adresses this problem can be found in this link below:

    Radial Load Flow for Systems Having Distributed Generation and Controlled Q Sources

    Abstract

    A load flow method that can be used for radial systems having all the common types of voltage control devices in addition to distributed generation sources is proposed. The method automatically adjusts the reactive power outputs of synchronous generators, switched capacitors, static var compensators and induction generators together with regulating transformer tap positions in an unified manner so as to satisfy the control characteristics of the respective devices by using a sensitivity based approach. In this context, a model for the induction generators that can be easily integrated with the proposed radial load flow method and a new approach to pre–calculate the sensitivity of node voltages, to regulator tap changes, are presented. Test results are provided to demonstrate the effectiveness of the algorithm.

About Distributed Systems

Distributed computing is a field of computer science that studies distributed systems. A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal. A computer program that runs in a distributed system is called a distributed program, and distributed programming is the process of writing such programs.

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