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Discrete Event Simulation - Science topic

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I have a well-described planning problem at a conceptual level, and I know how to model it on software. However, I do not precisely know how to sufficiently document the discrete-event simulation model, which is the result in this case. For instance, do I need to describe the underlying deterministic model mathematically first? I appreciate any suggestion for a guide in regards to this issue. Leaving a comment with a reference for a good paper that does the same helps handsomely. Ideally, your example addresses a capacity planning problem.
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Hello Mr Hafez, i have a paper that presents the results of a simulation. What i did is first explain the basics of my simulation, for example the map, map size, i had sources of cars so I added their explanations and a mathematical protocol of connection. You can also put the mathematical problem that you solve even before in the introduction and has a small detailed text from the state of the art.
Then i began presenting the variations and cases of my simulations and each one with its algorithm. Then the results of my simulations and discussion.
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I would like to know what validation techniques do people in the real world supply chain industry use. Something that is not very sensitive to time series data. Currently I am testing MAPE and paired t-test. But these tests are very sensitive and shows really high error. Any test that is not sensitive?
#simulation #discrete-event modeling #DES #agent based modeling #simulation modeling
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What statistical method would you suggest for time series data comparison Jorge LUIZ Sagayama ?
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A repository to aggregate a set of reproducible and reconfigurable codes and notebooks for testing various task placement policies for edge and fog server networks.
The simulation models are based on two of the most powerful python-based simulation modelling frameworks, namely salabim and simpy.
The systems that are modelled cover the basic types of task placement problems in edge computing servers. The models are useful for managing a network of edge computing servers.
There are animation and GUI options which are indispensable in simulation modelling.
The uploaded models are templates for building simulation models for a variety of edge network policies. Researchers who research task and server placement problems in edge computing would find the models useful.
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Just uploaded a model- load_balancing_with_mobllity_aware_task_placement.py -It models an edge network of three edge servers, with mobile and stationary user equipment. The task placement policy assigns computing requests to a) the nearest edge server and b) to the least utilized server. This implements a policy to reduce network bandwidth usage while ensuring load balancing within the edge network.
The model with other examples is on GitHub
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Hello everyone,
I am currently developing a small simulation model of an assembly worker pool in which I would like to consider randomly occurring absenteeism due to illness. Meaning: if one of lets say 17 workers is ill, he becomes unavailable and the Pool capacity is dynamically set to 16. After recovery, the worker becomes available again and the Pool capacity is increased by 1.
The model shall be based on historical data, which are available in the following structure (see excerpt @attachement).
The Pool Capacity is set every 8 hours with each shift change with the following logic (triggered by schedule):
- Create a list of all worker, that belong to the next shift group
- For each worker which is available (workers have parameter called “available”):
o determine randomly, if worker gets ill (using randomFalse(average chance to become ill, e.g. 2,5%, see above)
o If worker becomes ill, assign a value from custom distribution (bases on observations for the number of absent days per illness) for the number of unavailable days and create a dynamic event which will set the availability of this worker back to true after this number of days
The Pool capacity is set to the value that equals the number of the remaining available workers in the list
The model looks like this (see model overview @attachement).
On the first glance, the model works as intended. However, after 50 replications I aggregated the simulation data and compared the simulation result with my real data (table @attachement). I found out, that the model indicates, that ~41% of the shifts are staffed with 17 workers (= highest rel. frequency) while the real data show that 44% of the shifts are staffed with 16 workers (= highest rel. frequency of real data).
Something in the model concept does not seem to fit, otherwise the relative frequencies would somehow match in a better way, right?
Does anybody can tell me, if my current approach makes sense or am I overlooking something crucial? Is there a better approach to model this kind of problem?
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I agree with Christopher C Kelly , there may be non-random factors that contribute to absenteeism. There may also be auto-correlation between employees' absenteeism.
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Assume we have 5 service blocks in a system that requires the same resource unit. Say service block A and service block B have a service time of 1 minute each. Now I decide to combine these two blocks calling it service block X with a service time of 2 minutes. What should happen to the overall service time of the system? Will it go lower or will it remain the same? and why? Any proof from literature?
My experiment shows that the overall service time reduced.
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It will stay the same. No proof needed, it's obvious, but you can try it in simulation software - that is a good way to develope intuition about discrete event simulation.
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I am new to ARENA simulation and I have the following problem. I will describe the manufacturing system that I want to model.
I have the following manufacturing system (see attachment 1)
There are two different queues, in queue 1 there is only order type 1, and in queue 2 there is only order type 2. Depending on the type of order, either order type 1 or order type 2 has priority
  • Order type 1 is processed first/has priority at machine 1 (process1) if machine 2 (process2) is off
  • Order type 2 is processed first/has priority at machine 1 (process1) if machine 2 (process2) is on
  • If machine 2 is off and there are no orders of type 1 in the queue in front of machine 1 then order type 2 will be processed at machine 1
After order type 1 is processed it is disposed of, and order type 2 goes to machine 2 (process2)
But there is also another condition. Machine 2 is only turned on when there are 3 orders in the queue in front of it. If there are less than 3 orders in the queue in front of it, machine 2 will be turned off.
  • Machine 2 can only be turned on when there are 3 orders in front of it. So It has to wait until machine 1 is done processing all orders of type 1 before it can start processing orders of type 2.
  • if machine 2 is off and there are no orders of type 1 and machine 1 is processing order of type 2 and suddenly an order of type 1 arrives. Machine 1 will then finish processing the order of type 2 and will start processing the newly arrived order type 1. Once this order is processed it will start processing orders of type 2 again. This goes on until there are 3 orders of type 2 in front of machine 2 and it is turned on. Once machine 2 is turned on, machine 1 will give priority to order type 2 until machine 2 is turned off again.
so my question is how do I model this manufacturing system. I have made kind of a start (see attachment 2) but I'm to ARENA and just can't seem to figure it out.
Any help would be appreciated.
Thanks in advance.
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In order to switch on and off resources you must use schedules. For the priority of
entities you can use queues (as a block) and then you can switch to priority queue rule. I hope this helps.
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Hello,
I'm fairly new to ARENA and I have the following problem:
I have two queues in which, in each queue, a different order type arrives (both having an arrival rate of exponential 10). Order type 1 is processes by machine 1 and leaves the system. Order type 2, is first processed by machine 1 and then by machine 2 and then it leaves the system. (See the picture attached)
I’m new to ARENA and I have tried multiple times to model this process, but it is just not working. So I could use some help with the following
1. The orders (order 1 and 2) stay in the queue in front of machine 1.
2. machine 1 processes order type 1 or order type 2 but it gives priority to order type 2 when machine 2 is turned on. If machine 2 is off then order type 1 gets priority.
3. Machine 2 is only turned on when there are at least 3 orders of type 2 in the queue in front of it.
I have no clue how I can properly model this. I would appreciate it if someone could help me
Thanks in advance.
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this is the entire problem:
There are two different queues, in queue 1 there is only order type 1, and in queue 2 there is only order type 2. Depending on the type of order, either order type 1 or order type 2 has priority
  • · Order type 1 is processed first/has priority at machine 1 (process1) if machine 2 (process2) is off
  • · Order type 2 is processed first/has priority at machine 1 (process1) if machine 2 (process2) is on
  • · If machine 2 is off and there are no orders of type 1 in the queue in front of machine 1 then order type 2 will be processed at machine 1
After order type 1 is processed it is disposed of, and order type 2 goes to machine 2 (process2)
But there is also another condition. Machine 2 is only turned on when there are 3 orders in the queue in front of it. If there are less than 3 orders in the queue in front of it, machine 2 will be turned off.
  • · Machine 2 can only be turned on when there are 3 orders in front of it. So It has to wait until machine 1 is done processing all orders of type 1 before it can start processing orders of type 2.
  • · if machine 2 is off and there are no orders of type 1 and machine 1 is processing order of type 2 and suddenly an order of type 1 arrives. Machine 1 will then finish processing the order of type 2 and will start processing the newly arrived order type 1. Once this order is processed it will start processing orders of type 2 again. This goes on until there are 3 orders of type 2 in front of machine 2 and it is turned on. Once machine 2 is turned on, machine 1 will give priority to order type 2 until machine 2 is turned off again.
How can i model this?
Thanks in advance!
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My research is based on energy efficiency, I'm starting to write my Master thesis and I'd like some opinions of which software focused on energy efficiency is the best to use as a simulation tool of a manufactury plant/factory (discrete event simulation).
The aim of the work is to seek ''what-if'' scenarios of possibles savings at the energy perspective only and compare it to the real world.
I've read about Arena, Flexsim, EnergyPlus and Matlab but I don't know which one suits me best for this purpose.
Anyone got any opinions on this and suggestions for softwares (preferably free ones)?
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matlab is the most flexible because you can do everything yourself.
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During AM process, progressively activation of elements can predict the temperature/crystallinity history, including surroundings heat losses and than this data could be used to determine the deformation as well as the residual stresses within Abaqus AM plugin as one can do from user subroutines like UMATHT -> UMAT ? Are there any differences in term of results or convergence one have analyzed?
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There are very few people working with AM Plugin. Perhaps, in my opinion, results would be more reliable than the traditional method. However, I don't have sufficient data to support this claim.
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System simulations have been designed using MATLAB / Stateflow program. I want to calculate the execution time of the simulations under different system conditions for the purpose of comparison. Note that when calculating the execution time using tic and toc commands, each time it gives different results as is known.
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This is a typical problem. A general purpose computers assigns the processing time intelligently. The objective of computer is to process multiple programs at a time. Please note high priority programs will get more attention than lower one. Please try to change the priority of execution and check. But still I feel it would extremely difficult to compute the exact processing time in a system running many programs.
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In my model, the entities that are being created are supposed to be held in a Hold module and then be released on a regular basis, e.g. every 6 hours. So, I would need the Hold module to hold all entities that come in over the course of 6 hours and then release them all at once and start holding the next entities for another six hours and release them all at once and so on.
What kind of signal or condition do I have to use in the Hold module to realize this?
Thank you for your answers!
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Hi, I am new to Arena, so had a basic question. Whenever Hold module is triggered then only one entity is released , so how can one modify it to release all the entities?
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The multi-analysis modeling of a complex system is the act of building a family of models which allows to cover a large spectrum of analysis methods (such as simulation, formal methods, enactment…) that can be performed to derive various properties of this system. The High-Level Language for Systems Specification (HiLLS) has recently been introduced as a graphical language for discrete event simulation, with potential for other types of analysis, like enactment for rapid system prototyping. HiLLS defines an automata language that also opens the way to formal verification.
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The first ever formal model or can say a high level language for system specification is Transition System in paper "Formal Verification of Parallel Programs" written by Robert M. Keller Princeton University 1976. . This model was proposed to formally specify parallel programs. Many of the models emerged after it such as Automata Theory, Timed Automata, Hybrid Automata, Model Checking tools specific languages are based on the original labeled transition system (LTS). The new languages like HiLLS or Business Process Model and Notation from Object Management Group and many others are basically evolved from early LTS.
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Hi, I am doing a research project about UAV assisted VANETs, and I need to simulate a computational offloading algorithm in this type of network, so could you guide me to a network simulator that fits best to my work ?
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You can refer to The comparisons among the proposed papers are given in-terms of the simulator they have used. My suggestion is to go for INET and VEINS. In INET you will find more more mobility model to characterize UAV's mobility.
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I need to change this automatically generated title
Modelling a Hybrid Supply Chain using Discrete Event Simulation Modelling a Hybrid Supply Chain using Discrete Event Simulation CAHIER DU 391 Modelling a Hybrid Supply Chain using Discrete Event Simulation
in
Modelling a Hybrid Supply Chain using Discrete Event Simulation
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Dear sir, press on your artical and go to edit button then new window will opened that contained all paper information you can change the title and any other information you want to change
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Let say in a 10-day simulation, I can use the "Record" module to measure the "count" of arrivals, etc. Then, using one module for each day would return the count arrivals for each day (please see the picture).
However, if I have a simulation with 100 days, using the record module manually would be extremely time consuming (if not impossible). So, is there a better way to automatically return the statistics for any specific time unit (e.g., day, week, etc.)?
Any idea or hint would be greatly appreciated!
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You might try to write your input to a CSV file through the ReadWrite module. You first need to create a CSV file on your computer, then an output file in Arena by using File module under Advanced Process. After creating the output file, you could use the ReadWrite module in your model. If you assign two columns as 'Replication' and 'Arrivals' in the module, it would automatically write the requested information to the CSV file. I believe the link below might provide you more insights on how to implement this module.
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In Arena simulation, how can one utilize different types of resources in parallel (simultaneously)? For example, if a patient (as an entity) is in bed (i.e., the entity has already seized the bed as a resource), how can we add nurse's walk-around (when the nurse, as another type of resource, checks on the patient in regular time intervals)?
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Dear Alireza Boloori , yes, this would be one way to do it. You can also use process "clone" or you work with the process "signal" + "hold" and use the signal to create or seize the nurse.
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Osgood et. al's SD method has been used extensively over 50 years.
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What direction are you looking for development? linguistics or technology?
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Fading degrades the communication system performance due to a loss of signal power without decreasing the noise power over some or all the signal bandwidth, the received signal fluctuates, varies in intensity at each instant, increases and decreases through nulls and zeros of voltage. The probability of experiencing fading with the concomitant bit errors as the Signal-to-Noise Ratio (SNR) drops on the channel limits the link performance. Multipath fading (MF) affects most forms of radio communications links in one way or another. MF occurs in an environment where there is multipath propagation, and the paths change for some reason, resulting of propagating multiple versions of signals transmitted across different paths before they reach the receiver.
Paper:
Sharda B, Bury JSA (2008). Discrete Event Simulation Model For Reliability Modeling Of A Chemical Plant. Winter Simulation Conference.
Hu W, Sarjoughian HS (2005) Discrete-event simulation of network systems using distributed object computing. SPECTS'05.
Digital Modulation in Communications Systems. An Introduction, Agilent Technologies (2001)
Padilha R, Martins B I, Moschim E (2016). Discrete Event Simulation and Dynamical Systems: A study of art. BTSym'16, Campinas, SP – Brasil, December (2016).
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it's little complicate
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I want to do discrete event simulation in MATLAB but if anyone can provide their answer in R or Julia it would also be helpful
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You have to use a fixed step simulation using simulink if you want a discrete time simulation.
But if you want a simulation guided by events, you have to use StateFlow (https://it.mathworks.com/help/stateflow/index.html) and model a Finite State Machine.
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Hi
I am looking for a problem/topic that can be improved using Discrete event simulation for Final year project.
I wanted to do with Luggage handling process at the airport but there won't be many differences between as-is model and a to-be model.
Thanks
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I have 74 papers on Research Gate that discuss problems solved by applying DES. These include air traffic control, vehicle traffic control, train system control, sonar detection network, parallel and concurrent computer systems, and much more.
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I'm trying to model a case where a machine stops working if the queue of the respective process reaches a certain level (max level) and starts working again if queue of the respective process drops below a certain level (min level). In other words, I want to turn off machine 1 if the queue of machine 2 reaches 10 and want to turn it on again if the queue of machine 2 drops below 5.
I also added an Arena model to better explain the instance.
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Actually, I want to calibrate the relationship between distance to delay.
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@Kalpit Girishbhai Soni i want to also do the same help regardig this.
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I implement a discrete event simulation model namely "EOQ" in AnyLogic from https://www.runthemodel.com/models/2662/
I am going to optimize the parameters by minimizing total inventory cost. Therefore, I have to construct a function (one of the agent component in AnyLogic) in order to be able to root the total cost.
Currently, I have constructed a function and root the total cost (i.e. root.inventorycost()), but the total cost results in the same value whenever the parameters change.
is it possible to root the total cost when the model only has events, parameters, and variables? how to do it?
Thank you
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Rather than taking the square root of a model parameter COST introduce a new posiive valued parameter SQRTCOST with the property that the square of SQRTCOST equals COST.
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There are many software for system modeling such as MATLAB/Simulink, AMESim, Dymola, Easy-5 etc. They are comparable in terms of functionality. Some are decent for combinations of different type of modelings; for example AnyLogic allows you to combine SD with ABM.
Is there any in which combining SD with DES is possible?
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Dear Behzad Minaei,
I think you should take a look at the language Modelica for describing dynamical systems. There are also good open source implementations like JModelica, see http://www.jmodelica.org
You find good teaching material here https://www.xogeny.com/about/
and Mark Tiller has also written a couple of books and one recent book is an e-book for free. http://book.xogeny.com
I have myself used this software to develop applications in biotechnology during the last 5-6 years. Can take some questions if you need.
Best wishes
Jan Peter Axelsson
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discrete event simulation
energy simulation
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I have been working with different discrete event simulation software. (Delmia Quest, Plant Simulation, Simio, Arena) My personal selectrion is Siemenes PLM Plant Simulation and Simio.
For mechatronics engineering courses I use plant simulation due to OPC connection with PLCs . We model a manufacturing cell that has Siemens PLC and Rockwell Automation PLC, we connect the model in plant simulation with them to obtain a model that work as a monitoring system. In the other hand, it helps students to improve their programming skills with simtalk. Nx, Process Simulate and Process Designer (part of Tecnomatix Portfolio) are used in robotic and industrial automation courses.
For industrial engineering courses (Facility Design) I use Plant Simulation due to it's integration with AutoCAD (FactoryCAD and FactoryFlow add-on) analysis compatibility. In the other hand, Simio is a very useful and powerful tool to teach: process design, process optimization and production planning due to its ease of modeling.
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Say: Cars are used as entities first, but in latter procedures, people inside the car(which is randomly distributed within each cars) are entities.
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Every "Create" module gives unique entity. Alternatively, you might use "Assign" module to give attributes to the entities created from a single module.
Best Wishes
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I have one process and two resources A and B that makes the process in the same time. However, they have different process time? How I do this at Arena Software? In addition, the entity has to go in the two resources.
Thank you!
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yes there is a way. Assign one attribute with different value for each resource (for example, resource A could have processtime=1, and recourse B could have processtime=2), using assign box. 
then go to expression, add one row and name it (for example, processingtime), then specify the number of rows (2 in your case since you have A and B).
click on rows under "expression values", then in row one enter the expression for the processing time for recourse A, and in row 2 enter the processing  time for recourse B.
Now, go to your process, and fill out the logic box, once you finish, in the Delay Type, select "expression", and in the expression box, type the expression(attribute), in the example that i gave, this will look like, processingtime(processtime).
and this should do the work, don'f forget to change the units (minutes/hours) since I usually forget. and I might forgot some steps in this explanation, so feel free to contact me for any farther illustration.  
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In one of my paper, a reviewer is asking the simulation environment including network topology, traffic assumptions.
here how should I respond to the question???   does the simulation environment means simulation tool or something else??
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The simulation software, Methods.
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Respected Sir,
 sir in OPNET MODELER 14.5 i have made a PSTN model in a campus network of 10 KM . I have taken two PSTN softswitches and is connected by PSTN trunkOC12. further traffic region is defined.
Also its application profile,QOS profile and its traffic profile is defined.and when
config DES statistics is run with 10 minutes duration and with kernel type preferences  error has come which was attached in given file.
Sir in case of PSTN model WHAT WILL BE THE VALUE OF PREFERENCES .
sir please tell how we define this value in case of different types of network model,please explain in detail as i think due to this value the simuation is not running.
sir please give reply and explain me its basics of defining preferences for different types of models in OPNET 14.5
Preferences means from Edit--> Preferences option comes from there Discrete Event Simulation option comes there some value has to insert so as to simulate the model which we make. How to define that value for different models like for VOIP for ethernet or for PSTN. please explain it in detail.
The error which is coming is attached with this mail.
thanking you
Ritesh Sadiwala
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you have to take education version of opnet modeler and then to load it as otherwise only its license version is available
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DEVS (Discrete Event System Specification) is a modular and hierarchical formalism for modeling and analyzing general systems that can be discrete event, continuous state and hybrid continuous state systems.
Most modelers who are familiar with DEVS see the view point of DEVS as a modeling formalism forgetting the DEVS simulation protocol.
The clarification needed here , is if we recollect and readjust our mind set to DEVS including the Simulation Protocol are we scientifically right to presume DEVS is a domain as well as a formalism. 
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DEVS is discrete event systems modeling formalism. To justify it we must look to the roots and then we will see that this term is coming out of simulation. Therefore understandings exactly of this part researchers are major. Protocol could be part of specification. DEVS cannot be used for continuos systems specification. There are other methods. 
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There are some methods in order to determine warm up period in discrete event simulation, i.e. welch's method, SPC method.
  1. Is there any method used on finding run number (replication) in discrete event simulation?
  2. If yes, which one is outstanding?
  3. In simulation modelling, firstly which one (warm up period or run number) must be determined?
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Regarding simulation, the number of replications determines the width of your confidence intervals (reduces variance). The limiting factors will be computing time and expense. Assuming that performing N replications achieves a satisfactory estimate of mean performance as required by the user, performing more than N replications may be an unnecessary use of computer time and considerable expense. However, performing fewer than N replications could lead to inaccurate results and thus to incorrect decisions being made. 
There are three main methods found in the literature for choosing N: Rule of Thumb (Law & McComas 1990), a simple Graphical Method (Robinson 2004) and the Confidence Interval (with Specified Precision) Method (Robinson 2004, Law 2007, Banks et al. 2005). Law and McComas (1990) recommend running at least 3 to 5 replications. This rule of thumb is useful for telling users that relying upon the results of only one run is unwise. However, it makes no allowance for the characteristics of a model’s output, so although running 3 to 5 replications may suffice for one model it may be woefully inadequate for another.
In general, The Confidence Interval (with Specified Precision) Method is the one chosen both statistics wise as well as its capability to be adapted into an algorithm for automation for testing using artificial and real models. This method runs increasing numbers of replications until the confidence intervals constructed around the chosen output variable (e.g. mean queue length) using the t-statistic, are within a (user) specified precision. This allows the user to tailor the accuracy of output results to their particular requirement or purpose for that model and result. This method assumes that the cumulative mean has a normal distribution, (which is true under the Central Limit Theorem when the number of replications is large).
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Hi, hope all of you are having a good time. 
I'm new in Arena (extremely new), and 'cause I'm planning to simulate a roundabout, I have no idea how to start. 
For example, I don't know if use a kind of "pair" for each route like, Create and Dispose and put a Process Module in the center, then connect the Create modules and Dispose ones. 
UPDATE #1: Well, the roundabout problem is quite simple.
I have 4 intersections with thier own flow properties, like time arrival, time in the queue, types of vehicules. and we have off course the Server wich is the roundabout trying to attend the four ways (paths or intersections).
My doubt is, how can I model it in rockwell?.  For example I was thinking about to represent each way as a pair of Create and Dispose.
My doubts are:
  • What kind of elements appart of Create and Dispose elements, can I use to represent the flow showed in the pic?
  • How can I verify if a vehicle can get inside into the roundabout or have to wait?
  • How can I show a report of the results and get the Poisson distribution?
  • How can I animate it?
I already have the queue parameters for each ways, as I mentioned.  Sorry for have too many doubts, I just found this site a good way to learn and improve my knowledge between other teachers and students.
PS. Sorry for my english.
Thanks for reply 
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Dear Jeancarlo,
I think you can use conveyor to simulate the roundabout. The car has to wait for available space to join the roundabout as an item has to wait for a space to join the conveyor.
Best wishes,
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Arena simulation: how to release all entities (not resources) after certain time and start over again as a new day? (5 day simulation)
Current state: Entities are in the queue and the process is carried over the next day when resources become available. How do I clear all entities and resources in the system each day? 
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If you need to clear all process, resources and every statistic, you might restart as a new replication and run as many replications as you want.
If you want to release all entities from every queue but you don't want to refresh statistics, you could use the pick up and dropoff blocks using trigger entities every time you need to do that. Pick up and Dropoff blocks are in the advanced process panel.
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Good Morning.
I am working on DEVS and I search for some Java-based simulation tool that supports the Dynamic Structure DEVS (DSDEVS) formalism. I have worked on MS4ME but I suspect that this tool does not support DSDEVS, i.e., reconfiguration of the simulation on the fly. May you suggest me some tool that suitably supports DSDEVS?  
Thank you since now.
Best regards,
Valdemar.
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As a user, you can adjust the simulation runtime as you want.
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We can use historical data test or hypothesis testing to validate a model. But when generate a new model that doesn't has an existing (new system), what method that we should use?
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In my opinion a model is an abstraction, taking into account only the parts and variables interesting to us, of a system. Therefore, a model always has a system. Obviously the system can be totally abstract, not real, and then the model would be equal to the system (model and system would be just the same).
Obviously if the system is not real, or if it is real but no data can be obtained from the system, the validation cannot be made based on real data. In the first case validation is not needed, since by definition the model is good, as it is equal to the system (just verification is needed). In the second case, hypotheses must be made in order to estimate data (estimated data), which will be used to validate the model. In this case the model is validated to a system consisting in hypotheses, and therefore the model could be perfectly validated (fitting with the data obtained from the hypotheses) but non corresponding to the real data (data which is unknown by the moment).
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I'm about to do a parallel discrete event simulation, my case study is time series volatility prediction with Hidden Markov Model.
 Can anyone introduce me some related works about parallel implementation of HMMs?
 I will be more grateful if there was a Parallel discrete event simulation using HMMs.
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thank you Mr mittal.
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Background: 
I am trying to pick a resource from set 1 and when it picks a resource from set 2, it will pick a resource based on first resource from set 1. Let's assume set 1 resource set is comprised of  R1, R2 & R3 and set 2 resource set is comprised of R4, R5 & R6. If an entity chooses R1 resource (by random, cyclical etc) is must choose R4 (and not R5 or R6). 
I understand that, in such cases, the specific resource can be selected. But how can I link both of the resource sets?
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I have done by using set index, before that I saved an attribute, which was later called while using a different set. And it worked. But thanks for your suggestions
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I am a phd student of computer science working in WSN. I came across your paper. I have installed INET and MIXIM in omnet++. I want to use 802.15.4 nodes with aodv routing protocol but it does not provide any option in it that I know . Can you kindly guide how to do this ?
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Dear Beenish Ayesha Akram, I agree with Joseph to use NS-2 or NS-3. I have no idea about omnet++. Sincere apologies.
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I am implimenting the LEACH protocol on ns2.35. The protocol was added successfully in ns2.35. But when runnig the script leach-test i got the error.
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The destination has no listening model. If your destination is TCP it should has a sink application. If any one is sending to this node it should be listening at that time. Try to check your source and destinations and let destination start before sources.
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I would like to calculate distances between nodes and for that I would like to find position of nodes. Then by distance formula I can calculate distance. So please help me to find to position of nodes in omnet++. I am working purely on omnet++ not on its frameworks or simulation models.
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this code i am using it on my castalia network simulator using omnet++, it is finds all the nodes position,,
for(int i=0; i < (int)(theSNModule->par("numNodes")); i++)
{
VirtualMobilityManager *nodeMobilityModule = check_and_cast<VirtualMobilityManager*>(getParentModule()->getParentModule()->getSubmodule("node",i)->getSubmodule("MobilityManager"));
x[i] = nodeMobilityModule->getLocation().x;
y[i] = nodeMobilityModule->getLocation().y;
trace() << "********** x ["<<i<<"] " << x[i] <<" y [" << i<< "] " << y[i];
// trace() << "**********" << x[i] << " " << y[i];
}
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I am conducting a discrete event simulation research for the management of patients flow in an emergency unit of a healthcare system but pose with a problem of getting a suitable software that can help me analyse the data obtained.  
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Hi Umar M. Modibbo,
AnyLogic is an often preferred simulation software recently by academia. It enables users to multi method modelling. You can find samples of AnyLogic models including emergency room model in this link:
Best wishes.
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Sir,
I have made a PSTN model  and assign various attributes to it but on compiling it i am getting error which  is attached below.please tell me what is its meaning.
also what value is to be given at "Network simulation Repositories " at open a new project then press Edit > preferences then search for network then scroll down for a label "Discrete event simulation and then to "Network simulation Repositories " so that the program gets configure and simulation runs.
As when its value is given stdmod  or stdin the program is not running similarly if we give its value as 0 again it is not running.
so please tell its value so as to run the simulation
the error is attached below
thanks
ritesh sadiwala
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sir ,
thanks for your reply
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I work with the assessment of production system configurations with respect to operational, economic and environmental performances.
A production system configuration is meant to be a facility with specific equipment, layout, numbers of operators, etc.
The assessment involves a comparison of the configuration being studied with other alternative configurations (for instance, a case "yes, new equipment" VS "no new equipment, status quo"). The comparison is being done through discrete event simulation.
Now, my doubt is on how to make sure that the evaluation compare the two cases fairly. 
Beyond the fact that the two systems get supplied with the same input distribution of pieces to process, I wonder if I have to make sure that the two systems are evaluated and compared with the same level of performance operations wise (e.g., same yield, same efficiency).
To me, this is to make sure that both systems' operations are managed by the same people having the same expectations in terms of efficacy of operations management. 
An example of this approach is to optimizing both systems firstly and then compare the resulting performances. 
What are your thoughts on that?
Every idea and source is most welcome. I will particularly appreciate previous experiences in discrete event simulation of production systems and considerations about design of experiment in the context of production systems and operations.
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I think you are probably looking at this the wrong way round. It is not really a meaningful comparison if you start with assuming the two production systems are working at the same level of efficiency. You need to make the comparisons based on requirements of demand (quantity and variation) and input requirements (materials, labour etc), plus any relevant constraints.  You can then use (operational) efficiency as the measure to compare the systems. Of course you still need to decide how to measure "operational efficiency" in the cases you are studying.
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There are free and paid tools that develop discrete event simulations , in particular we are looking for one that is easy to use but at the same time contains all the functionality required for such simulations.
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I think that the question "...what is the best software tool for develop a discrete event simulation?" is an unfortunate example of a wrong question.
There is NO best software tool. Moreover, the particular discrete event simulation package is NOT that important. There are literally dozens of commercially available DES packages, e.g. simul8, arena, promodel, simio, anylogic, flexsim, processmodel, etc, etc, as well as free cloud-based packages. They all are powerful enough for most practical applications, all have a similar simulation engine, but differ in the user interface, program coding, visualization (2D or 3D), commercial license costs, etc. There are quite a few published reviews that compare the dozens of DES packages on the various criteria.
The MOST important thing is the simulation methodology and the model design.
How  to convert a problem from a descriptive language (often fuzzy and unfocused that the clients use) into the concrete simulation techniques?
Does the model answers the real practical questions, or the model is built for the sake of modeling in itself?
 Does the model help to clarify a real issue (often unspoken because of clients' limitations to state it clearly using disciplined logic thinking)?
These issues, I believe, should be addressed rather than specific DES package.
The developing of a library of simulation techniques for some typical applications & problems /situations that can be converted into any DES package would be very useful.
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Is there any precise definition for the agent-based simulation? If a discrete event simulation (DES) is load-driven, i.e., decisions are made from a load (e.g., product, customer, etc.) prospective, can we consider it as agent-based?
There is some paper suggest that DES and agent-based simulation are separate categories. Why?
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First of all, just to mention that exist a great confusion on this because there is a great confussion regarding on what is a model and what is an implementation of a model.
To perform this classification is needed to be focused on the model and not in its implementation, that can be diverse.
Having said that, a DES model is a model where the EVENTS rules the dynamic behavior of the processes that  pictures our system understanding, the EVENTS are the elements that modifies the state's variables. Whit this idea, the models can be represented easily with DEVS, Petri Nets or Specification and Description Language (among other formal languages). In these formalisms is quite easy to detect that the EVENTS are the key element that rules the behavior, hence here we are talking of DES models.
In contraposition to this we can define a models where the EVENTS do not rule the dynamics, as an example, those models defined by Forrester diagrams (system dynamics) where a continuum modification of the state variables takes place. In that case the paradigm used to define the models is different (here we are not talking of DES models but continuous models).
MAS systems  (AB simulations) are those simulations where the entities (i.e. agents) can own a great complexity, can learn, and can modify his behavior depending on his knowledge and the information they obtain from the environment. The definition of this kind of models are based on the description of EVENTS that impact on the agents modifying its states. Hence MAS is an specific DES model where exists specific elements that are more complex, but, the dynamic modification of the states are mainly based on EVENTS, hence MAS are a DES models.
If you are interested on see a formal representation of a MAS system see the papers I attach. On they are clearly detailed why (although is not the purpose of the papers) a MAS model is a DES model.
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There are different methods (Dimensional Consistency Test, Event Validity Test, Sensitivity Analysis, Historical Data Validation, ...).
What is the best method for validation and verification of discrete event simulation?
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Have a look at the Winter Simulation Conference Proceedings Repository. There are many good papers on the topic (looking at the topic from a theoretical and a practical perspective).
When I teach this topic to my students I also refer them to Stewart Robinson's book "Simulation: The Practice of Model Development and Use" where this topic is discussed in very much detail for DES.
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I am looking for examples where a mistake in a simulation (discrete event or agent-based) has led to wrong predictions and consequently caused big trouble (e.g. problems with productivity; loss of money).
I know that people usually do not write about failures in the scientific literature. But I remember very vaguely that during my PhD studies I read about some examples. Unfortunately I cannot recall the authors/titles of these papers.
Your help is much appreciated. If possible, please provide references.
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Hi
Hmm, here is an example, where the simulation was PHYSICAL (in the beginning
of the 1960'ies the computer power simply did not allow a simulation).
The Vajont Dam in Italy was completed in 1959, but the risk of a landslide was
known and a physical model was made and simulations were made. Unfortunately,
the experimenters underestimated the speed by which the landslide would occur,
so instead of a 25 m. tsunami a 250 m. tsunami was created. The city beneath the
dam, Longarone was destroyed and 1909 people were killed.
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Now I work and try to optimize the vehicle scheduling and routing problem using arena Simulation but need to know and learn other softwares and approaches.
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AnyLogic with OptQuest Optimization Package (additionaly): http://www.anylogic.com/
To my mind AnyLogic is the most convenient tool for simulation in transport and logistics.
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Guaranteed results
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PRACTICE and a basic degree or course related to the theory being implemented by that simulation so that you can figure out any abnormality of results.