Science topic

Network Modeling - Science topic

Explore the latest questions and answers in Network Modeling, and find Network Modeling experts.
Questions related to Network Modeling
  • asked a question related to Network Modeling
Question
19 answers
Hello, did these two articles discover the same theory? My academic performance is too shallow to be sure. I think that although the terminology used in these two articles is different, their views and ideas are similar. The difference is that the "dynamic interactive process network" mentioned in this article adds the viewpoint of "psychological network model" to several sentences. Thank you!
Relevant answer
Answer
Hi,
The second paper is a published one and discusses two theories on the same concept based on factors derived from factor analysis:
"controversy centers on Nef’s popular Self-Compassion Scale (SCS) and the argument that compassionate self-responding (CSR) and uncompassionate self-responding (UCS) are a single dimension versus the argument that they are two semi-independent, unipolar dimensions, with UCS, not refective of “true” self-compassion."
The Author proposes "The link between CS and UCS will depend on the timeframe of measurement, current circumstances, and individual differences."
The author tests his hypothesis based on secondary data analysis of published data sets. He tries to propose an alternative "process" approach and remarks that the factorial approach does not help. But the question is the process approach in the subheading Practical implications are not substantiated with any data analysis. He also makes a statement "Instead of allowing individual human beings to disappear into a statistical fog of between-person variability, it seems kinder and more compassionate to give each individual and their own lived experience a voice". This statement appears only impressionistic but uses a term "idionomic" .
The paper makes an attempt to highlight a need to understand an individual on one to one basis however, the way is not substantiated and is unclear.
The First Paper :
Not published
In-text citation absent.
Terms are not defined as citations are absent.
Most of the narration is hence, purely subjective.
The analysis is mainly based on Cognitive Behaviour Therapy and Psychodynamic formulation as it appears so from individual case evaluations.
  • asked a question related to Network Modeling
Question
1 answer
Mechanisms leading to the spastic movement disorder (SMD) as a positive symptom of the upper motor neuron syndrome are not yet fully understood. All, the underlying disease, the (spinal) lesion level, the lesion location within the brain, affected descending (parapyramidal) motor tracts, disrupted sensory input etc. seem to be more or less relevant for the emergence of a SMD.
Is there any research on computational network models of spinal/supraspinal spasticity on the base of current neuroanatomical and neurophysiological data known to be of relevance for the develoement of a spastic movement disorder?
Relevant answer
Answer
See Project:
"A Computational Model for Epidural Electrical Stimulation of Spinal Sensorimotor Circuits "
  • asked a question related to Network Modeling
Question
16 answers
Dear scholars,
i am looking for a code in Matlab or R-language to run the wavelet-Neural Network model. please if any of you have done a project relating to this model please share with me. you can also share the paper representing the outcome of your work, so that it can be read and cited appropriately. if you have done this code in another software other than Matlab or R-language , you can also share with me. i can learn such software. Also if you have another resource where i can get codes or learn how to develop this code please you can put the information here. Thanks scholars
Relevant answer
Answer
You may also check out this software package which contains several tools for time series analysis, such as change detection, wavelet analysis, monitoring, and forecasting (written in both MATLAB and Python):
An earlier version has a MATLAB Graphical User Interface as well:
If you use GitHub, the updates, comments, and new releases can be found here:
I would be happy to walk you through the code and its implementation if you need help
Best regards,
Ebrahim
  • asked a question related to Network Modeling
Question
5 answers
Dear all,
I would like to know if it is possible to use SAOMs (Stochastic actor oriented models) to analyse weighted networks?
Thank you in advance,
Léa DAUPAGNE
Relevant answer
Answer
There seems to be a less ised feature to handle ordinal values. It is discussed here: http://lists.r-forge.r-project.org/pipermail/rsiena-help/2013-July/000272.html
  • asked a question related to Network Modeling
Question
4 answers
I Interested in to work in gene network modeling thus I need to know what is future of gene network modeling in agriculture
thanks
Relevant answer
Answer
interested
  • asked a question related to Network Modeling
Question
2 answers
Hi everyone,
I am focusing on pore network modeling of a two-layered nonwoven medium.
Considering you have a two-layered fibrous medium with a given gap between and you intend to extract the representative pore network. How need to deal with the intermediate pores at the gap?
Experimental observations shows a dip of oil saturation at the gap.
I have enclosed a snapshot of the geometry. I wonder except extracting the network of the whole geometry, is there any alternative techniques?
For instance, is it possible to stitch the representative networks to each other upon extraction? If the answer is Yes, then how should the throats at the interface be defined in terms of connectivity, length, diameter, etc?
As shown it is an unstructured network and it is not easy to deal with the pores at the interface.
Thanks,
Relevant answer
Answer
Hi Arash,
I just noticed your answer to my question.
Thanks for the response. I already found a strategy to deal with the issue. The networks were virtually generated and put in different gap sizes to each other and the whole network was extracted, subsequently. I also ran single and two phase simulations and replicated the oil saturation drop within the gap, observed experimentally - the main objective I had planed for.
P.S. I found some of your works relevant to my current work and referred to them in my publication and those coming.
Thanks again,
Abouzar
  • asked a question related to Network Modeling
Question
3 answers
Recently an external collaborator performed for me a GC/MS on my samples, using Glucose and Glutammine with all C labelled.
The related data consist in peak area of each metabolite/isotopomer. I tried to analyze these data by INCA (a toolbox of MATLAB), but I need to find a metabolite network model that describes the pathway that I want to investigate (e.g. TCA Cycl and Glycolysis)
Do anyone know were I can find network models?
I would like to recive any suggestions about better MFA software analysis as well as INCA.
Thanks in advance
Relevant answer
Answer
As you seem to already have the Mass isotopomer data of different metabolites (obtained from 13C feeding experiments followed by GC-MS), This is the typical workflow you can adopt ahead:
1. Do mass correction to remove the contribution of natural abundances of isotopes (You can use IsoCorr or similar tools- https://academic.oup.com/bioinformatics/article/28/9/1294/312644).
2. The resulting Mass isotopomer distribution data can be used to map metabolism of your cells (see here how we did it
3. You can further define the carbon transition network in INCA or any other 13C MFA software (See tutorial as well as examples that come with the package).
4. Metabolic Modelling/Flux analysis in the platform needs - Substrate Uptake rates, Biomass components efflux rates (which you might have measured or borrowed from literature on your system). Your measured isotopomer data also goes as input while flux analysis. The model predicts isotopomer distribution and compares with your measured and provides the fit as statistically acceptable or not (You may need to play with the model iteratively until you get confidence on the flux values). More reading will help - https://www.nature.com/articles/s12276-018-0060-y and references there off.
Sounds a bit complex, but once you try one can master it.
Best wishes
  • asked a question related to Network Modeling
Question
4 answers
Dear all,
I would like to know if it is currenly possible to use temporal ERGMs (Exponential Random Graph Models) for analyzing weighted networks?
For now, it seems that software packages available to analyse TERGMs (tergm or btergm) only use binary networks.
Thanks in advance for your answer,
Léa Daupagne
  • asked a question related to Network Modeling
Question
4 answers
Hi all, currently carrying out some qualitative data analysis using NVivo and I was wondering how I could create a network model/diagram to show the relationships between my coding (such as a visual representation of: 'X is part of Y, Y results in Z' and so on).
Relevant answer
Answer
I believe that NVivo refers to what you want to do under the headings of "Mind Maps" and "Concept Maps."
  • asked a question related to Network Modeling
Question
15 answers
I am interested to simulate distribution networks with distributed generation utilizing custom controls. Simulink is quite versatile in control system design and is friendly for people preferring visual approach to programming. But I am not always satisfied with how it solves power flow for detailed network models.
Lets say that I am looking for more reliable power flow solvers, but with control system design versatility of Simulink (preferably with visual programming). Any suggestions?
  • asked a question related to Network Modeling
Question
11 answers
I am a physician and visiting research scientist at yale and together with my coauthors have published several studies in the field of psychology through Network Modeling and related analyses using r packages like bootnet, qgraph, NetworkComparisonTest, etc. I thought it might be a good idea to discuss different subjects related to this field, in a group. I am also interested in collaboration with other teams working in the field. Let's share our ideas, questions and suggestions in this group.
Relevant answer
Answer
Makes sense. Thanks for letting me know.
I hope followers of this discussion forum check your study and package,
which address an interesting topic in network analysis. Let's keep in touch!
Best Wishes,
Farhad
  • asked a question related to Network Modeling
Question
4 answers
In the context of complexity, it is well known that each change that is given to nodes or relationships in a network will give emergent properties, and I am looking for a way to model these effects.
Relevant answer
Answer
Thank you. There is one crucial aspect to complex systems that you probably already know but it is important to repeat it again and again.
Entropy.
The concept entropy enables us to measure the operational state of any complex system in existence without having access to its totality.
It is possible to observe just one signal generated by the observed system and from this signal -- using entropy measures -- to assess the operational mode and other properties of the observed CS.
I did propose and used the same approach to predict ventricular/TdP arrhythmias from ECG recording (signal) of the heart (CS).
  • asked a question related to Network Modeling
Question
1 answer
I work on a competitive social networking model and I want to use Gambit software to solve it.
  • asked a question related to Network Modeling
Question
3 answers
Since metabolic interactions are complex in multi-species systems, currently genome-scale metabolic models are applied to uncover the metabolism of each microbes. Then, can we build the cross-feeding models?
Relevant answer
Answer
It would be really interesting to use complex networks and mathematics based on them which is being developed by Albert-Lazslo Barabasi. He is the leading researcher in this area.
It is easily imaginable that the intensity of nodes -- representing various methaboloids -- and presence/absence of edges between various nodes that will represent interspecies feeding.
It can be accompanied by genomic networks activity as well. By manipulating of species composition, it is possible to uncover interspecies feeding and edges that represent it.
Alternatively, it is easy to imagine an agent-based model describe interactions of those networks. This model can uncover hidden metabolic interdependencies among networks associated with single species.
It sounds like an exciting scientific project.
  • asked a question related to Network Modeling
Question
21 answers
How can we increase the confidence for a new authenticated key exchange protocol in terms of the operational in the network model?
Relevant answer
Answer
I,agree with Shakir Tuleab
  • asked a question related to Network Modeling
Question
7 answers
I am a student of MS Mechanical engineering at Islamic International University Islamabad. I have started my research on pore network modeling of porous media. Please guide about the mathematical modeling of pore network.
Thanks
Relevant answer
Answer
Percolation theory for the beginning, maybe?
  • asked a question related to Network Modeling
Question
5 answers
I'm looking for a recent review article that demonstrates what topics are in the focus of network modelling in the last years. I'm particularly interested in applications to socio-economic systems and ideas from econophysics.
Relevant answer
Answer
Thomas Neusius this paper you have shared looks interesting. will try and have a look soon!
  • asked a question related to Network Modeling
Question
19 answers
Psychology has developed to the stage of "network model" and "process-based therapy". Psychology is about to enter Newton's time. If you are really interested in psychology and want to achieve something in the future, then you should focus on the frontiers of "network model" and "process-based therapy" (PBT).
The latter, in particular, will be the future of psychology, to which all schools of psychology converge. I have written a new theory of psychology, that is, from the development of PBT, please do have a look, this is very important。
Relevant answer
Answer
Mine too...lol.. Thanks for the discussion. Have a great week!
  • asked a question related to Network Modeling
Question
11 answers
Recently I came across of studying protein fluctations in Normal Mode analysis, Most of it was conducted in Elastic Network Models (Gaussian or Anisotropic). What insights we can develop by studying the protein fluctuations using ENM or quassi rigid decomposition. How is this different than Molecular Dynamics Simulation? Guide me through the entire concept.
Relevant answer
Answer
Of course, I believe an all-atom MD is more useful than an NMA (or more specifically a coarse-grained Elastic Network Model (ENM). One should be wary of some caveats though. An all-atom MD has a much more accurate physical representation of a polymer in addition to the effect of solvent, so the conformations generated along a trajectory are in principle more realistic than an NMA. Yet we are usually trapped around the initial conformation in an MD simulation, so some enhanced sampling MnD simulation method might be necessary (especially if the molecules undergoes large conformational transitions).
1) The NMA utilizes one single conformation and "simulates" oscillating vibrations around this conformation (by connecting Hookean springs between residues, usually using a pre-defined spring constant). That is the core feature here. You don't supply any MD simulation trajectory. Just one single initial conformation is enough.
The thing with "energy-minimised" structure is, well, you "assume" that your initial conformation is already "energy-minimised". Because if we have some X-ray structure, for example, we naturally assume that this is the native state of a biopolymer. This might not be always true. Yet it is usually the best starting point. It might be useful to energy-minimize the structure prior to NMA though. I haven't done it myself, but if you're doing an all-atom NMA using a force-field, I read this is even more important.
After you conduct the analysis (Bio3D is fine and I see the documentation and features are much detailed and practical than the last time I checked. I use ProDy though, mostly because I am accustomed to Python), you "decompose" the motion (as described by the Hessian matrix) into individual modes. These are defined by eigenvectors and eigenvalues. Here an eigenvalue is representative of the "frequency" of a mode of motion (so high eigenvalues correspond to low frequency motions). We can talk about low against high frequency motions here. Low frequency modes of motion are usually termed "global" and involve collective movements of structural domains - which may be important for enzyme catalytic activities, for example. High frequency modes are more "local" and usually denote so-called structural "hot-spots" which may be important for ligand binding or stability.
2) Once we get the eigenvectors, it is possible to calculate the fluctuations of each "node" in this system (which are residues). See the documentation of ANM 2.1 server for more explanation:
1) The first 6 modes are always missing, because these correspond to rigid body translational motions which are always there for any system (we are not really interested in this, are we?). The fact that Bio3D reports these is methodologically accurate but they're not really informative.
2) Yes, I think so. But we're almost always interested in a subset of modes and this is also dependent on what aspect of the intrinsic dynamics we're investigating (in the context of biological meaning of low versus high frequency motions).
3) Frequencies plot, I guess, indicates the mode frequency (each bar denotes a mode)
I found the following lecture notes quite formative by the way:
  • asked a question related to Network Modeling
Question
3 answers
I am performing pore shape analysis and creating pore network models of segmented microCT scans of carbonate plugs.For this purpose I require a parameter to estimate the complexity of a single pore.
Relevant answer
Answer
It is all about the shape aberration from the circle, isn't it?
If you can discretize the image to triangular mesh, determine the distance range between the closest and the most distant vertices from the pore barycenter. Calculate weighted average distance between the barycenter and every vertex in that ring. Sum all distances between the neighbouring vertices in the ring and divide with the circumference of weighted mean distance from the barycenter. What you get is a dimensionless positive real number that tells you how many times is the rim of that pore longer than rim of the circle with the radius you calculated as weighted average distance.
If you can't triangulate the image you must work with the intensity values from the image. A circular pore has small area of the transitional intensity gradient in the edge region. A complex pore must have greater area in the same region. If you divide the first one with the second one and take the square root out of it, you should get the ratio analogue to the mesh based solution.
In both solution you should figure out how to compensate for inaccuracy due to discretization.
  • asked a question related to Network Modeling
Question
2 answers
I'm thinking the problem of mapping applications to geo-ditributed data center. However, most of work focuse on the network heterogeneity. And these network models are in old fashion. So I wonder any new network model is available to apply. And economic theory can be adopted on minimizing latency on geo-distributed datacenters.
Thank you.
Relevant answer
Answer
Hi,
In a distributed DCN, Spine leaf model is the latest model for massive scalability while Fog model optimizes bandwidth for service provisioning.
  • asked a question related to Network Modeling
Question
4 answers
I  would ask if anyone can help. I have a huge EEG dataset, which I would used for training and testing Deep belief network model for predicting. I'm facing a challenge in the training this model using my PC and Matlab. I know that Matlab  2017 has Scale Parallel MATLAB Applications to Amazon EC2 Using Cloud Center, but not sure if it free for student and how to start doing this. Please help if you have any idea. Thanks  
Relevant answer
Answer
First: The MATLAB software should be licensed.
Second: Yes, EC2 version is not free. However, the price are optimal.
You can refer to below link for its functioning:
  • asked a question related to Network Modeling
Question
4 answers
I am using Bayesian network for modeling risks in construction project. referring to the article or the thesis"
Estimating cost contingencies of residental building projects using Belief networks"
Are the method used for defining the probability distribution for the root nodes and conditional probability tables for intermediate nodes correct?
is it applicable to use the average value of probability for each node and feed the network manually? in other word, by taking the average, we learn the network by taking the average for each node and enter these number manually.
Relevant answer
Answer
BTW you can combine the expert judgements and real database in to BBN, or firstly build the structure manually and then updating the structure by using evidences which are real databas. Hope it help.
Qing
  • asked a question related to Network Modeling
Question
4 answers
I need help to introduce me to some software that I can use for my research project. I just started doing a research about discrete fracture network to enhance in situ recovery of hard rock mining.
Relevant answer
Answer
Hi
The GINsim software is free and user-friendly (for logical modeling). To run the software, install JAVA. there is a manual in documentation part.
  • asked a question related to Network Modeling
Question
1 answer
In my domain of experiment out of three input parameters one parameter is qualitative . Is it possible to construct a neuron network model taking qualitative term in to consideration including quantitative input parameters?
for example input parameters are color(dark, fair,brown),height and age.
Relevant answer
Answer
I think you mean categorical/factor variables: you can use one hot encoding to preprocess them before passing to the neural network.
  • asked a question related to Network Modeling
Question
1 answer
I've seen some studies using pore network modelling and/or percolation theory with continuous time random work (CTRW) for modelling groundwater flow and mass transport, which is very interesting. I'd like to know comparing with classical methods, such as FE and FD with Advection and diffusion/dispersion equation (ADE), what is the advantage of this method? or for which kinds of problems, this method does better? And what is its limits or disadvantage?
Thanks a lot.
Relevant answer
Answer
Interessing question
  • asked a question related to Network Modeling
Question
4 answers
If I do pore ​scale modelling ​in a confined ​space for small ​plants or a ​reservoir, by ​direct pore ​space, ​reservoir ​modelling or ​network ​modelling using ​Navier-Stokes,​ Boltzmann ​method - is ​that valid for ​contaminant ​removal by ​using a porous ​membrane or can ​it be effective ​in water ​treatment? ​
Is it viable ​to succeed in ​near future in ​wastewater ​treatment areas ​as well? ​
  • asked a question related to Network Modeling
Question
14 answers
The original, and current, Internet design has been mostly based on an honor system for the end points. The model being that the connection is less trusted than the end points, as access to the end points was granted under an honor system — and usage rules were effectively enforceable.
Reality showed that this model was upside down for commercial operation. The end points are less trusted than the connection. In fact, even if usage rules are enforceable at some connection points, the end points cannot be controlled. Anyone can connect to the network. There is no honor system. Usage rules are in fact not enforceable, users can hide and change their end points. The solution is to introduce trust as an explicit part of the design, which trust was implicit when the Internet was based on an honor system.
Of course, updating the Internet design to fit its current operating conditions is useful not only to stop spam. Social engineering and spoofing attacks also rely on the old honor system where users are trusted. "Trust no one" should be the initial state under the new Internet paradigm. The bottom line is that trust depends on corroboration with multiple channels (see Trust, above) while today we have neither (a) the multiple channels nor (b) the corroboration mechanisms. So, we lack trust because we can't communicate it.
Current work [1 and following, see RG home page] by Ed Gerck and team includes these topics, proposals and tests to combat spam, spoofing, and denial of service, as well as information-theoretic secure authentication integrated with authorization for access control.
Relevant answer
Answer
Hello Albert,
Of course, when the spammer matches the user filters to PASS, also in the user device, the user gets the spam! And people may prove to be NOT on the Internet on a machine, and at the same machine can send an email AS on the Internet, which I also described. The Internet is a network of networks, no matter your not acceptance of it. You can study more, may be helpful on your job, or at least for discussions on RG. It is not enough to know the words, but what they mean.
Cheers, Ed Gerck
  • asked a question related to Network Modeling
Question
4 answers
Working with associating polymers to make physical gels, I often come across the label 'transient' for these networks. I was wondering if there is a way to determine wether a system is truly transient? I am aware of the transient network model in rheology which can help interpret data, but am wondering if there is a more direct way to determine the transient nature other than a correlation between this theory and experimental data?
Relevant answer
Answer
Dear madam,
Although my research work has a more chemical, small molecular weight background it might be of interest to you. With our system we looked at the temporary properties of the gels and analyzed these over the lifetime of the gelphase. As the lifetime of our gels was within several hours to days, we were able to measure this both through rheology and confocal microscopy. Both techniques can also be used for polymer gels. For determining the transient behavior of a gels, I would suggest a experimental approach were changing the conditions leads to different transient behavior.
Good luck with your research,
Wouter Hendriksen.
  • asked a question related to Network Modeling
Question
5 answers
I am currently analyzing collaboration networks in science. I have used SBM and ERGM to model a cumulative snapshot of the network. I know these methods alone are not sufficient to accurately model my network since it is a longitudinal network. I heard of Stochastic Actor-Based (or actor-oriented) Block Modeling (SABM) which can model my network taking into account it's dynamics in time. I have read some papers on it but have been unable to find a tutorial to guide me through its successful application on my data. Can anyone help? 
Relevant answer
Answer
You might find the lecture and notes from the Social Networks And Health at the Duke Network Analysis Center (DNAC) useful; includes R code, David Schafer did the presentation.
  • asked a question related to Network Modeling
Question
2 answers
I am trying to use Ieee802.15.4narrow as a base for my simulation. I want to get the RSSI value, but I don know how to print the RSSI when a packet is received in a node.
I am relatively new in Omnet++ and I am wondering if anyone could help me.
Relevant answer
Answer
Hi Ameneh, i'm trying to calculate the RSSI in the same base simulation too, can you solve it?
  • asked a question related to Network Modeling
Question
1 answer
I am trying to estimate decompression time for fuselage with multiple chambers connected in serial and parallel network. Can we use pipe flow network model for this kind of compressible flow analysis?
Relevant answer
Answer
Look at this doc it may be helpful for your topic. Good luck.
  • asked a question related to Network Modeling
Question
5 answers
I have 3 layer deep network model. Each model has hidden layers. could some one suggest is there any criteria to be followed for setting the hidden layer size. 
In one paper i read we have to set the hidden layer size to 2/3 times the input size. 
Is there any criteria required for setting hidden layer sizes. Or arbitarily can we take any hidden layer size
Relevant answer
Answer
Size and count of hidden layer can be properly set only with empirical reseach. There is no technique which could produce optimal neuron count or hidden layer count.  Good rule of thumb is to perform crossvalidation and test/evaluate model on outsample data.
The more data for training you have, the bigger size of hidden layer can be. Try to divide training dataset length by connections count. If you have more than 300 you are on good path to success.
  • asked a question related to Network Modeling
Question
3 answers
I tried MATPOWER but I don't think it's helpful for this.
Relevant answer
Answer
The Anderson book on power system stability has all the generator parameters you need.
  • asked a question related to Network Modeling
Question
4 answers
I have a BN model in which there are four nodes. They are Job Arrival Rate, CPU Usage, Memory Usage and Resource Utilization. CPU usage and memory usage are dependent on Job Arrival Rate. Memory usage is also dependent on CPU Usage. Resource Utilization is dependent of CPU Usage and Memory usage. I have marginal probabilities of all the nodes. I want to calculate conditional probability table of the last node i. e., Resource Utilization which is dependent on both CPU Usage and Memory Usage. Please help me out.
Relevant answer
Answer
Hi, it is very easy. Use GeNIe software which is free. Create your network with the nodes that you just mentioned. Define the relationship between nodes using the Arc (from parent to child node). Then in each node's properties define the probabilities. Then GeNIe will calculate the conditional probabilities automatically. It is a very convenient software for any types of BN modeling. If you need more details on how conditional probabilities are calculated in BN or how to use GeNIe, read my paper "A Bayesian network model for evacuation time analysis during a ship fire". I am sure it is very useful. 
Regards,
Parvaneh
  • asked a question related to Network Modeling
Question
2 answers
PS: I have single time point gene expression data for around half of the gene in the signaling network.
Relevant answer
Answer
You may check these papers:
A Tutorial on Analysis and Simulation of Boolean Gene Regulatory Network Models
Boolean Modeling of Genetic Regulatory Networks
Boolean Network Model Predicts Knockout Mutant Phenotypes of Fission Yeast
Modeling mechanistic biological networks: An advanced Boolean approach
  • asked a question related to Network Modeling
Question
13 answers
like adding a temporal component on existence of an edge?
Relevant answer
Answer
I guess what you mean is to have a network which is parameterized in discrete time index say: t->t+1  etc. where what is on the edges and nodes is supposed to vary in time or may be as you say even the number of connections or edges and at another extreme case where also the number of nodes could vary.  Yes, I see no in principle problem at letting all these things vary in either different kinds of mixed problems , or separately one at a time. If you are interested , I have some unpublished notes for some years ago about the bottle neck problem where I've let the number of connections vary N(t) in time and derived a diffusion problem with varying diffusion coefficient- could be a common work here. 
  • asked a question related to Network Modeling
Question
4 answers
Large-scale tunnel aerodynamics is generally one-dimensional, whereas near-scale airflows can be three-dimensional, especially due to buoyancy forces due to fire, or in complex geometries such as station boxes, or near obstacles such as vehicles, message signs, cable trays, etc.  With the ever-increasing computational power available, it has become possible to solve the near-scale features by a three-dimensional CFD code, and keep the solver for large scale tunnel airflows one-dimensional, and use a code to pass outputs of one code to the inputs of the other in an iterative way.   Where the type or format of data on each code is different, the effort of passing data between the 1D and 3D codes outweighs the benefits.  What has been your experiences of this process, and what obstacles have you encountered?  How do you see the future of multi-dimensional airflow network models?
Relevant answer
Answer
I think there are two main issues.
Firstly, going from 1D to 3D means that a 3D field needs to be created. It is often not clear what form such a distribution should take. There is quite a lot of work related to turbulent inlet conditions which show that even generating fully developed turbulent inlets can be tricky. In the general case the assumption that the inlet turbulence is fully developed may not be correct and so the implementation of the 3D inlet will be even more challenging.
The other issue is related to uncertainty. In my opinion the uncertainty bounds of a 3D simulation are likely to be larger than those for a 1D simulation. If you have a 1D system code in which you wish to replace one part of the system by a 3D local simulation, the modelling and grid uncertainties of the 3D part will undoubtedly add to the overall uncertainty of the system being modelled.  The 3D part will undoubtedly add useful insight into the part being simulated locally however the overall behaviour of the whole system may well become less clear.
  • asked a question related to Network Modeling
Question
3 answers
I'm preparing a framework based on context- awareness , i need to model data (location from GPS, time, daily events from calendar, and human activities) using Bayesian Network or decision tree for inference high level context.
Could you help me to know which of them is suitable to me and candidate the suitable software to me?
Relevant answer
Answer
The WEKA API (developed in Java) offers Bayesian Network implementations (K2, TAN) as well as several decision trees methods (ID3, J48, CART, etc.).
  • asked a question related to Network Modeling
Question
16 answers
Actually, Hello, I am working on Vehicle-to-Infrastructure (V2I) communication over heterogeneous wireless network. I would like to develop a handoff algorithm and simulate it using matlab.
I really need help!
Thanks
Relevant answer
Answer
Can anyone help to provide  useful guides (or codes) on the implementation of  MADM Access network selection in OPNET. My previous works have been implemented in MATLAB, but need to measure some parameters (e.g number of handover, delay, throughput, etc) using discrete event simulator. 
  • asked a question related to Network Modeling
Question
4 answers
Once an information flow (IF) can be represented as a process, can we measure your complexity as a network?
According Brandes, Robins, McCranie & Wasserman (2013), in order to think in terms of network first is necessary to have elements (E) and processes (P) of a network model: phenomenon (E), which passes through an abstraction (P), making the concept of the (E) which may be represented (P) and data network (E).
Taking the IF as a broad phenomenon, can we introduce the concept of network processes, which can be viewed as a web of interdependent tasks or activities, its products, which are more than the sum of its components and the participating organizations, can be understood as a network of people and communications?
Which measure can be more appropriate in this case?
Relevant answer
Answer
As in an complexity measure, you must first consider the usefulness of the metric. In essence, a metric should preserve relations in the real world (objective or intersubjective) in such a way that if X has relation R to Y in the real world it is reflected in the metric. It should also be possible to make informed decisions based on the metric in an activity performed by an actor that tries to achieve a goal. 
So, what kind of activities do you envision such a metric to be useful in? What kind of decisions do you want to make (e.g., alternatives) based on this metric? If you fail to envision this, then what good would a metric do? I can define "squarishness" as a criteria and arbitrarily start counting squarish objects in a region, but to what avail I do not know. The metric can be made both correct and meaningful, but hardly useful (unless I find a reason for counting squarish objects).
  • asked a question related to Network Modeling
Question
15 answers
I have to optimise paramters "(theta)" of a model of a railway network "F". This railway network model is given to me in the form of a MATLAB-p file, so it is a black box. I have been given two data sets from the model, input u and output y. The output of my railway network mode, "F" is say y_cap.
Then y_cap = F(u,theta). 
I plan to take my optimisation function so as to minimise square of error between y and y_cap that is (y-y_cap)^2 and tune the parameters theta. 
That is, objective function = (y-y_cap)^2.
Is my objective function convex or non-convex? How to comment on its convexity? 
Relevant answer
Answer
A convex function has a unique optimal value but not a unique point where this minimum is attained. Only STRICT convexity guarantees uniqueness of optimal solution.  So no worries of you have different points with the same minimum value. 
Of course as pointed by others two statting points are not enough. Try harder.
Another approach is to use a finite difference method to APPROXIMATE the Hessian matrix and check it is positive (semi)definite. This is the most definitive test within the approximation error of your difference method.
Gill, Murray and Wright, Practical Optimization, in an excellent reference to read on this.
  • asked a question related to Network Modeling
Question
3 answers
Dear all,
even myself, I always use MCMC to deal with all ERGMs I faced. However, today my Boss asked me a very simple question: "Why must you use ERGM and always solve with MCMC?", suddenly I found that I had no answer. After that, I felt that this question is quite interesting and I am curious about it as well.
Does anyone have some convincing answers?
Thanks in advance.
Kuan-Wei
Relevant answer
Answer
Dear Andrey
MCMC is a method for searching a complex parameter space. In other fields people would consider gradient descent algorithms, genetic algorithms, and other stranger things. All of these could be good. I am thinking about whether they present any real advantages.... it is a good question but I am not confident in my answer. I will have to try some things!
  • asked a question related to Network Modeling
Question
4 answers
Hi everyone,
I had to draw a real-world network from a basemap in ArcGIS 10.2. After having added my shp files to a geometric network, I fixed the network build errors. Then, with the purpose of determining the degree of each node (e.g., the number of edges connected to that node), I ran the Spatial Statistics Tools->Utilities->Collect Events function. This gave me a table with the ICOUNT values, which correspond to the degree I was looking for.
My problem: the number of vertices worked out by the Collect Events function is far lower than the number of vertices my network actually has.
1) How can this be possible?
2) How could such function miss any point? 
3) What do you think I could do to spare me the use of some network modeling tool?
PS: Using the Join function to see what vertices are not mapped in the ICOUNT table is out of question as the ObjectID key of the two tables does not refer to the same points.
--
Thank you for your time and dedication.
Relevant answer
Answer
Francesco, I am not that experienced with ArcGIS 10.2 and geometric networks to answer your question directly. But I am a friend of the Python module Networkx, which has a lot of functions and algorithms for network and graph analysis. And,  for the sake of ArcGIS users, the module can import shape files.
With this module installed you can run the commands in Python console (or standalone importing ArcPy):
    G=nx.read_shp('your_edges.shp')
    print degree(G)
Export your edges as a shape file of polylines. The read_shp function will extract start and end nodes, labels them with the corresponding coordinate tuple, and construncts the network.
Since nodeIds will be derived from coordinates, you are able to reconstruct which node in the network belongs to which real world position.
Most outputs are lists and dictionaries. So your are free to process the results according your needs.
  • asked a question related to Network Modeling
Question
8 answers
Please mention names & web-Links of the software tools for computer network reliability assessment. 
Relevant answer
Answer
It offers a detailed fine-grained modeling of the energy consumed by the computing servers, network switches, and communication links.
  • asked a question related to Network Modeling
Question
4 answers
Edwin S. Shneidman (On the Nature of Suicide, 1969) proposed that 6-8 people are significantly affected by every suicide. This has generally become accepted as a benchmark in suicide prevention/postvention, but does not seem to have been the subject of much research. This "ground zero" for suicide loss comprises all or some of the victim's closest family and friends, which made up her/his social network in life. Communications theory studies social networks and one model (see link below for example) conceptualizes a "support clique" with about 5 members with very frequent contact with an individual and a "sympathy group" of about 12-15 people with at least monthly contact. Has any of the communications work been used in studies of suicide survivors?
Relevant answer
Answer
Tony
A very good question, but I have no data or information.
  • asked a question related to Network Modeling
Question
4 answers
how can i configure a network based on voip using opnet modeler 14.5 ??
Relevant answer
Thanks Akhilesh sir,
Sow can i  get above version of OPNET i.e. V17.1 and what are major differences in both the versions i.e. in 14.5 and in v17.1.  how can we learn to use this modeler as i am new to this and there is no proper guidance available here in BHOPAL MP who can help me in learning the Modeler. Kindly provide me the direction of using this modeler.
thanking you
  • asked a question related to Network Modeling
Question
4 answers
Respected All,
Recently I have installed OPNET with visual Studio 10 in windows seven(64-bit).
I want to work on WLANs and for this i try to design network model given in the tutorials and also follow the same steps but at the end when i press the run button of OPNET after setting all the output variables gives bundle of error and did not show any of the graph i am attaching the tutorial as well as error sheet.
I am very thankful if you guide me that how can i simulate any network model in OPNET accurately....Please refer me some books materials so that i can get expertise in this tool and able to do my work.
Thanking you in anticipating.
Relevant answer
Answer
For now i'm using the practical opnet user guide #BOOK
  • asked a question related to Network Modeling
Question
4 answers
I have weights and biases for my network model, training in MATLAB tool. I implemented the network model in MATLAB code and I compared the results with sim() function unfortunately I am getting wrong results.
Anyone implemented the network on microcontroller?
Relevant answer
Answer
Can you specify your question a bit further? Your current statement is quite vague.
Some usefull additional details would be:
What microcontroller you are considering, what type of system you want to emulate, and if you want to implement the model in the controller for co-simulation, control or fault detection?
If you'd like to switch to a specific microcontroller, it could be usefull to investigate the programming languages and toolboxes available for that component.
Also, try to make sure the code, structure and model order is suitably chosen in Matlab (with acceptable fit in cross-validation), since otherwise you'll be implementing an useless model for your purpose.
  • asked a question related to Network Modeling
Question
4 answers
I would like to apply network flow techniques to solve evacuation planning problems.
Relevant answer
Answer
Hi Tanka,
Have a look at www.evacmod.net , you have there many resources on evacuation modelling. The list of models on the market is here: http://www.evacmod.net/?q=node/5 and you have the results of a survey on the most known and used software here: http://64.186.156.50/~evacmodnet/?q=node/2574
Cheers,
Enrico
  • asked a question related to Network Modeling
Question
2 answers
This question is related to the measure of estimation and forecast accuracy in (freight) transportation network models.
input data : origin-destination (O-D) matrixes at the European regional NUTS2 level for different transportation modes (road, rail, inland waterways). These matrixes contain tons transported for a given year between each O-D pairs. These matrixes exist  for different types of commodity, but this is of less importance in my question.  Consider this input as the "observed real-world" data.
Model : the matrixes are merged, so that I have one single matrix per category of commodities, that includes all what is transported by the three modes. Several mode-choice and assignment procedures are applied in a network model. Using a sample of 5% of the OD pairs, the model is calibrated for each mode-choice/assignment model that is tested, in order to reflect the "observed" modal-split found in the input data for the sample. The calibrated cost functions are then applied to the total matrix.
Output : For each mode-choice/assignment model, I retrieve the tons that are allocated to each OD pair, for each mode. I can also retrieve the tons that are assigned to each link (road, rail, waterway) of the network, but I've no observed counts along these segments, so that I cannot use this output.
It comes out that, even if classical estimators such as R2 (computed on a per O-D basis : observed tons / tons obtained by the models) can be very similar from model to model, the distribution of errors can be very different.
Question : I would like to compare the (relative) quality of the different models I test. A came over a series of estimators used in forecast accuracy (MSE, MAE, MAPE, MsAPE, sMAPE,...) and more recently MAPE-R and MASE, but I'm not sure that these estimators can be applied to the problem I describe here. Does someone have any experience with this ?
Relevant answer
Answer
Thank you for you answer Ali.
MLE is an option to fit the model. It could indeed be used in a modal choice context. However my problem is not to find the best modal-choice model formulation, but is to compare the (relative) performances of several models applied to a same dataset.
  • asked a question related to Network Modeling
Question
2 answers
Dear everyone:
I have a question regarding  the permutation traffic pattern.
Background
Since the seminal work of Gupta and Kumar [1], extensive efforts have been devoted to study the throughput capacity of wireless networks  restricted to the so-called permutation traffic pattern. It is widely considered in the literature that under the permutation traffic pattern, the source-destination pairs are matched at random in a way that the destination sequence is a  permutation of the source sequence, e.g., [1-3].
Question
My question is as follows.
A general permutation may have fixed points. An element is called a fixed point of a permutation, if it is mapped to itself under the permutation. E.g., for the permutation :(1,2,3)->(2,1,3), 3 is a fixed point of this permutation. 
Since a permutation may have fixed points, the permutation traffic pattern literally allows a source to select itself as the destination of the traffic flow originated from this node. It is notable, however, it does not make sense that a node transmits to itself in a wireless network. Besides, in this case, the throughput capacity would become infinite, since the transmission to oneself does not use the wireless medium.
Therefore, the term permutation traffic pattern might be misleading in my understanding. And I am wondering whether this misleading term can be replaced by the derangement traffic patternSince a derangement is a permutation without any fixed point, the confusing case of talking to oneself can be avoided. 
Does anyone agree with me or have  a better understanding/explanation on the permutation traffic pattern?
Best,
Yin
Reference
[1] P. Gupta and P. R. Kumar. The capacity of wireless networks. IEEE Transactions on Information Theory, 46(2):388–404, March 2000.
[2] Niesen, Urs, Piyush Gupta, and Devavrat Shah. "On capacity scaling in arbitrary wireless networks." Information Theory, IEEE Transactions on 55, no. 9 (2009): 3959-3982.
[3] Garetto, Michele, Paolo Giaccone, and Emilio Leonardi. "Capacity scaling in ad hoc networks with heterogeneous mobile nodes: The subcritical regime." IEEE/ACM Transactions on Networking (TON) 17, no. 6 (2009): 1888-1901.
Relevant answer
Answer
Dear Prof. Martin
Thank you very much for your  support and nice answer. 
Best wishes,
Yin
  • asked a question related to Network Modeling
Question
5 answers
I'm working in modifying existed protocol (OLSR) and I want to add this modification into OPNET modeler 14.5 to check if it works well or not. 
References are better for helping and also any other tools 
Relevant answer
Answer
Check out this book "Unlocking the Power of OPNET Modeler".
You should find it on Google books and Amazon. 
  • asked a question related to Network Modeling
Question
3 answers
Traffic model.
Relevant answer
Answer
That depends a lot on whad to you understand by traffic model.
If you are talking of internet traffic :
- Modeling Internet Backbone Traffic at the Flow Level - http://infoscience.epfl.ch/record/475/files/BarakatTIDO03.pdf
- A Survey on Internet Traffic Identification and Classification: http://www.crysys.hu/~szabog/index_files/traffic_application_classification_survey_draft.pdf
Student survey, but quite interesting: From Poisson Processes to Self-Similarity: a Survey of Network Traffic Models - http://www1.cse.wustl.edu/~jain/cse567-06/ftp/traffic_models1
Multimedia traffic models:
- A Survey of VBR Video Traffic Models - http://www4.ncsu.edu/~hp/Savera3.pdf
- A survey of multimedia streaming in wireless sensor networks: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4738464&tag=1
If you are talking about vehicular traffic:
State-of-the-art of Vehicular Traffic Flow Modelling -http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.106.9913
On the Impact of Trafc Models on Inter-vehicular Broadcast Communications: http://www.infres.enst.fr/~drossi/paper/rossi06medhocnet.pdf
And that goes on and on.... which traffic domain you are talking about?