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In compressible flows, would improvements based on the SST K-Epsilon turbulence model , such as the use of AI,be a more promising direction in engineering. ten or thirty years from now, will the most commonly used model be the Reynolds stress model or its deformation, or will DES be the most commonly used simulation method.
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Possibly you should have a look at
Baumert, H. Z., Universal equations and constants of turbulent motion,
Physica Scripta, T155, 014,001 (12pp), doi:10.1088/0031-8949/2013/T155/014001, 2013.
Also have a look at the attachments.
Feel free to ask specific questions!
Best,
Helmut
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I am making a DES in order to produce levulinic acid
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Pedro Nakasu
do you know how long should i mix it for?
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Generally, while performing antioxidant activities, we evaporate the solvent in which extraction is performed to obtain the dry weight of sample. The dried powder is then used to make dilutions, and we carry out TPC and TFC on them. However, while using a non-volatile solvent like DES or glycerol, we cannot evaporate the solvent used for extraction. Hence we are unable to obtain the dry mass of the plant extract. How should the procedure be performed and what sort of calculation should we then use to get our final answer in mg GAE/g DW or mg RE/g DW.
The equation formally used is:
C = (c x V)/ m
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Theoritically speaking yes, but you have to use the graph to know at which level dilution is benificial. Good Luck in your work
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wireless sensor networks
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Dear Chindiyababy Uthayakumar,
Take a look at the following sources below:
QKD – How Quantum Cryptography Key Distribution Works:
_____
Quantum key distribution:
What are the cybersecurity risks to current cryptographic techniques?
Our cybersecurity infrastructure requires two different functions: authentication and confidentiality. Authentication allows distant users to trust their counterpart and validate the content of their exchanges.
It is mostly implemented by public-key signature schemes. Confidentiality is required for any exchange of private information. It is often performed in a two-step process. First the users have to exchange a common secret key.
This relies on another public-key protocol, the key exchange mechanism. The secret key is then used in a symmetric key encryption scheme. Both functions therefore depend on similar cryptographic techniques, known as asymmetric or public-key cryptography.
Cybersecurity is much more than the underlying cryptography. All current hacks and security failures do not come from a weak cryptography, but rather from faulty implementation, social engineering and the like. Today, we trust the cryptography, and fight to get the implementation right.
Unfortunately, this is about to change. The point of cryptographic vulnerability today is public-key cryptography, based on algorithms such as RSA or Elliptic Curve, which are used both to authenticate data and to securely exchange data encryption keys.
The very processing power of the quantum computer can solve these mathematical problems exponentially faster than classical computers and break public-key cryptography.
This means that the currently used public-key cryptosystems are not appropriate to secure data that require long-term confidentiality. An adversary could indeed record encrypted data and wait until a quantum computer is available to decrypt it, by attacking the public keys.
We need quantum-safe cryptography today.
_____
Quantum Key Distribution: A Networking Perspective:
_____
The case for Quantum Key Distribution A proven system for future-proof data protection.
_____
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I want to predict whether a certain molecular pair will form DES or not, is there one or more parameters that can be calculated from MD simulations from which I can know if this molecular pair will form DES or not?
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Dear Marwa Abd El Kader Zaater, computer simulation is widely used to predict DES formation. Would you please specify the system under investigation. Please have a look at the following links. My Regards
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While implementing DES and AES using python I wane to measure memory consumption,CPU utilization.
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Hello everyone,
My goal is to know how accurate is my simulation using the Wall Modeled Large Eddy Simulation (WMLES) S-omega and to calculate the total turbulent kinetic energy.
Therefore I would like to know if I'm resolving 80% of the turbulent kinetic energy with my grid and to do that I need to compute the SGS turbulent kinetic energy and compute the ratio between the resolved and total turbulent kinetic energy (k_resolved / (k_resolved + k_sgs) )
Assuming the resolved turbulent kinetic energy can be calculated by:
  • k_resolved = 0.5 * (U_RMSE ^2 + V_RMSE ^2 + W_RMSE ^2 )
Is there a way to compute k_sgs using the various parameters given by Fluent ?
The turbulent parameters that Fluent has available are:
  • Subgrid Turbulent Viscosity
  • Subgrid Effective Viscosity
  • Subgrid Turbulent Viscosity Ratio
  • Subgrid Filter Length
  • Effective Thermal Conductivity
  • Effective Prandtl Number
  • Wall Yplus
The article referenced in the Fluent user theory guide is (PDF) A hybrid RANS-LES approach with delayed-DES and wall-modelled LES capabilities (researchgate.net)
According to the guide, the subgrid filter length is given by the equation (4) and the subgrid turbulent viscosity is given by equation (19).
Thank you for reading,
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Greetings.
Depending on the type of simulation that is performed, many features appear. In the “run calculation” tab, the variables can be extrapolated, and more parameters can be added. These are located by pressing the “other/add variables” button. In case what you need does not appear, it can be accessed through the console and even perform the operations you mention. However, there are many hidden options, perhaps you can find some more information in the user guide. Remember that it is commercial software, which means that it is closed source and many of the calculations are black box, so what you are looking to calculate would be very complicated.
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Hi everyone. I am using DES model to simulation turbulent flow with RE 6500. I am only getting one vortex and not getting any vortex shedding. I tried to use URans model, but it shows no vortices and only wake region behind cylinder. Please inform me whats effect of model on vortex shedding.? Will LES provide vortex shedding or there is some other reason of not getting vortex shedding. Thanks
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I do suppose that your DES model is looking for unsteady (time dependent) solutions?
regards
mico
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Most studies have focused on HBDs and their effects in processes involving DES. Is there a reason for such an inclination on the study of HBDs and not HBAs, especially in terms of biomass fractionation?
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Dear Regan Ceaser, I think the role of ChCl is beyond the economic factor. The attached file deals with aspects related to its role. There are other papers which take its polarity and molecule size as being key answers. Please find one important paper investigating this topic. My Regards
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Some authors are using a series of new alternative of ionic liquids, named DES and Ch-DES and claimed to overcome the disadvantages of conventional extraction methods. How these solvents overcome it? What are the main advantage and problems and issues related to these components for extraction of high value chemicals/ phenolic compound etc extraction from various bioresources ?
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The reason for the application of Choline chloride in DES as a replacement for ionic liquids is based on advantages such as ease of preparation, low cost of DES, environmental friendliness and ability to work at low temperatures to achieve similar results.
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the DES i'm working on is thymol:camphor
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Dear Nida Anis, thymol based DES's are hydrophobic. They have poor solvation power to salts such as sodium carbonate. This may explain the turbidity seen. My Regards
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Hi! I`ve got question about DESs. How can I proof the formation of DES? If speak about IR, which regions should I look at and which bands can indicate on the presence of hydrogen bonds? And one more question: the addition of water results full distruction of DES or water will only dilute DES? Is there any information about how much water I can add to the DES before it stop being DES and become "water and dissolved substances"?
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Dear Arina Levina thank you for your interesting technical question. The question would certainly get more qualified answers if you explained what you mean by DES. I had a hard time finding it out. When you check the Wikipedia entry on the abbreviation DES you find no less than 26 different meanings of DES on the English page, from "Data Encryption standard" to "Deep Eutectic Solvent" (https://en.wikipedia.org/wiki/DES).
Since you were talking about hydrogen bonds in your original question I assume that in your case DES stands for desloratadine, right?
In this context, please have a look e.g. at the following useful link which is freely available as public full text:
Improving mechanical properties of desloratadine via multicomponent crystal formation
For the stability of desloratadine in water, please also see the following relevant article:
Acid-base equilibria and solubility of loratadine and desloratadine in water and micellar media
It could also pay off to use the "Search" function of RG to find and access other useful references on this topic. Just search for "desloratadine" and then click on "Publications". This will result in a large number of interesting articles:
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If I prepared a DES from choline chloride (ChCl) by quantifying ChCl by some means, what effect will the water have on the final product? How will HBD-HBA interaction be effected? Will a DES be formed at all under these conditions?
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Dear all, if the question is still unsolved, please check the following documents. My Regards
10.1039/C8CS00325D
10.1002/anie.201702486
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Dear
Madem/Sir I Need Payload Encryption and Decryption With 3DES in Python And C Language Please This Code Is Very Necessary For Me Please Anyone Find out This Code For Me and Send Me 
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A python3 example
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My system consists of ionic liquids, aliphatic and aromatic hydrocarbons. Any suggestions and any script for calculation of viscosity?
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A patient with hereditary desminopathy (mutation Thr341Pro DES in a heterozygous state) with disease progression has a significant decrease in taste. How can this fact be explained?
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Probably affect facial nerve and glossopharyngeal nerve in the pons and medulla oblongata?
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Hi, everyone.
I am starting to work with fractionation of Biomassa by Deep Euthetic Solvents .
I came across a DES that is comprised of Lactic acid: Glucose:water (molar ratio 5:1:3), as in ref.
My problem beguns as I found out lactic acid is sold only as a 85% (w/w) solution. So when I do the math, I will have a surplus of water.
My idea is to do a reduced pressure destilation of the lactic acid to remove water and obtain pure lactic adic, and then add water and glucose on the proper molar ratios.
Anyone out there that has experience with that, is it the proper approach? Any other ideas?
Thanks.
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If possible, use pure lactic acid. The presence of water in the solvent must be calculated in terms of weight and may cause problems.
First, calculate the molar ratio that you want according to the molecular weight of each material.
Next, place all materials in a 50 ml vial container
Place the vial on the stirrer.
Set the speed ratio of the device to 200 rpm.
The temperature should be 80 degrees Celsius.
Depending on the material you are using, it will take between 60 and 90 minutes for the material to melt and form a clear, uniform solvent.
Once the liquid is clear, the eutectic solvent is finished.
In the sent images, the clear liquid formed is visible.
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We all know that cipher(algorithm) design is publicly known and only key is hidden. So if everyone knows substitution, permutation details what is the point to add these layers in any symmetric key encryptions algorithm ?
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A line of substitutions followed by a permutation has good “mixing” properties: Substitutions add to local confusion and permutation “glues” them together and spreads (diffuses) the local confusion to the more distant subblocks.
Modern ciphers tend to use linear or affine mappings instead of permutations, which allow them to achieve better diffusion in fewer iterations. Such networks are called substitution–linear (SLN) or substitution–affine networks (SAN). The block encryption standard Rijndael/AES is an SLN cipher.
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Dear All,
Which type of simulations is good to investigate the rotating stall in axial compressor? RANS, URANS, LES, DES, and DNS. Secondly, a single passage or multi passage is recommended for the investigation of rotating stall.
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Filippo Maria Denaro Thank you for your suggestion. I have enough computational power and i have checked papers too. some people used RANS, some LES and DES. I was thinking that which technique will give me the good results
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Hubble constant estimates from collaborations: Planck’s mission, SDSS-III Baryon Oscillation Spectroscopic Survey, DES Collaboration, H0LiCOW, Riess et al, Hubble Space Telescope are objective and not in doubt. It means that the Hubble constant describes two similar, but different physical processes, therefore objectively have at least two meanings. An estimate of the Hubble constant based on relict radiation describes the process of rotation of the space of the observed Universe, and an estimate of the Hubble constant which based on measuring changes in the distance to distant objects of the observed Universe (quasars, Cepheids, red giants ...) describes the process of rotation of substance in the space of the observed Universe. The Hubble constant with equal success presents two mutually exclusive hypotheses: the hypothesis about of the dark energy and the hypothesis of rotation of the space of the observable Universe. The hypothesis of the dark energy admits only one value of the Hubble constant and the hypothesis of rotation of the space of the observed Universe admits a multi-valued Hubble constant. Forecast: all estimates of the Hubble constant based on relic radiation will be grouped around its analytical estimate 1) 67.5577 (km / s) / Mpc, and estimates of the Hubble constant based on measurements of distances from distant objects of the observable Universe will be grouped around its second analytical value 2) 74.15 (km / s) / Mpc.
It can be assumed that the rotation speed of a substance with a mass density that is substantially lower than that of quasars, Cepheids, and red giants will be between 1) and 2).
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After the Big Bang, the space of the observable Universe made one incomplete revolution of at 345 degrees, and the substance in it made one complete revolution of approximately 379 degrees. https://hal.archives-ouvertes.fr/hal-02045149
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There are four general types of DES but i think none of them particularly address potassium carbonate based DES. Should it be regarded as a new type of DES?
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I think the classification by Abott is not somewhat to be strictly followed. There are many examples which does not fall in this category like non ionic deep eutectic (urea acetamide, lauric acid glycerol etc), magnetically separable DES etc. Recently there is a report of type 5 deep eutectics also in chem comm.
Coming to your question, if we somewhat relaxes the definition it may well be included in type 4 deep eutectics
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I need to synthesize high volumes of DES with choline chloride.
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Hi,
Yes, it is enough. Thanks.
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Hi!
I`ve read lots of articles "how to make DES", and that is what I`m interested in:
It`s absolutele clear that "to make DES you need just combine substance 1(HBA) and substance 2 (HBD) in a known molar ratio, then heat and stirring until homogeneous liquid is formed - congratulation - you`ve got DES!"
Ok, let`s try. I took ChCl and Oxalic acid in molar ratio 1:2, put them on water bath (80oC), made them constantly stirred. They formed liquid, I took them away from water bath and let them cooled. And they become solid immediately after cooling.
So where is the problem? I made it without water. Maybe they need some water ?
Or it`s normal that they become solid, and I need to carry out all my subsequent experiments at 40-50oC?
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Freezing point of Choline chloride:oxalic acid 1:1 DES is reported as 34 deg. C. So yes, it's normal and you need slight heating to make it liquid.
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I am working on a external aerodynamics vehicle CFD simulation in which I want to make sure, that the flow that actually hits my vehicle has a certain level of turbulence intensity. Therefore I am using a DES Spalart-Allmaras turbulence model. I set up a region further down in my flow volume in which I am adding a turbulence source in the form of modified turbulent diffusivity (no other option of defining turbulence possible) - the variable transported in the Spalart-Allmaras approach.
However I see major fast decay of this variable, starting right after its introduction to the field. Which parameters can I change to reduce the rate of decay of the modified turbulent diffusivity in my field - with the goal to keep it higher then a certain level for some time and thereby keeping a certain level of turbulence intensity.
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@Ha
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Menthol:lactic acid DES is strongly acidic, this negatively impact the extraction of acid labile lipophilic molecules such as lycopene from tomatoes. l wonder if it is possible to bring it to an almost neutral pH value. Does anyone have suggestions?
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Menthol is a colorless hexagonal crystals dissolved in acids, alcohol, ether and volatile oils. The acidity of methanol is controlled by selecting the solvent type
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Basically, biomechanical stent modeling can be divided into three areas. The first area belongs to the modeling related to the mechanical properties of the stent, the checking of the stress states of deformations, the arrangement of the voltage on the wall of the blood vessel, etc. and mainly these tests are based on the Finite Element Method (FEM). It is very important to carry out all the tests at this stage in order to find out all design defects in time, because any irregularity discovered later requires a return to this stage and a re-testing, and this can be a very "expensive" step both materially and temporally. In the second area, the influence of the stent design itself (for example, the shape and layout of the sticks) on the flow of fluid (blood) within the blood vessel is studied and is based on the computational fluid dynamics (CFD), an area belonging to the FEM. In the third area, it is also investigated and tested for the release of the drug in DES stents and its spreading through the bloodstream, penetration into the blood wall.
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I am not sure what is the question, but if you are interested in these topics, Simulia/Abaqus has quite a few stent examples you can take a look at. There is even a dedicated training.
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Modeling partially observable systems can be useful in many applications. There are multiple techniques and tools to model DES (Discrete Event Systems) and partially observable systems using Stochastic Timed Petri Nets. It would be good if we model the system using STPN for fault detection. Thus, my question is "Do you have any idea how to model partially observable systems using Stochastic Timed Petri Nets for fault detection?"
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Dear Guru,
I'm never implement a system in timed Petri net, your idea is an interesting fashion. Now I'm applying the techniques of other modeling languages with Colored Petri net for partially variable observation of a process design. such as:
May you get the solutions as soon.
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I want to obtain names of all the FTC of DES to write a survey paper about this subject. I know only three methods: Supervisory Control appraoch, control reconfiguration approach, hiding approach.
There is no literature reviews on this topic so the choice of articles is really a critical task.
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Specially, a journal of Springer named "Discrete Event Dynamic Systems" would be the good reference of your area of interest. I have also published a paper about this topic, though it is of SOA-based systems-"Fault analysis of service-oriented systems: A systematic literature review".
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- Are there places in the world where DID is integrated into culture (e.g. hmong shamanism) or appears in folklore?
- What are some places that are better and that are worse at recognizing DID?
- Does the whole world use the DES?
- When DID is diagnosed, what are the treatments in places other than America/Europe?
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"Rêve et chamanisme", ed Accarias l'Originel, Paris, 1998.
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It is known that the complexation of a quaternary ammonium salt with a metal salt or hydrogen bond donor (HBD) resulting in DES formation. The charge delocalization occurring through hydrogen bonding between for example a halide ion and the hydrogen-donor moiety is responsible for the decrease in the melting point of the mixture relative to the melting points of the individual components. However the DES is not form between TEAI and Glycerol at 80 C and in varying molar ratios i.e., 1:2, 1.4, 1:6 and 1:8. I would like to know the reason why DES is not formed in this case.
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The (usual 2 components as in your case) DES components do not interact through covalent or ionic bonds but via intermolecular forces (hydrogen bonding), inducing molecular alterations at the lattice units lowering the mp.
Since DES of glycerol /tetrabutylammonium bromide (and chloride) are fairly common (in various proportions) the Iodide ion (size and properties) may have some interference in those forces/latice ordering...Also, I do not know -(I am not an expert at DES preparation, but just using some of them)- DES including Iodide ions in their formulation (at least with glycerol based ones).
Hope it helps
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DES are often seen as green solvents, however, their chemistry and mechanism is still scarcely available. How do they posses lower melting and freezing tendencies in-comparisons to their original constituents? And what are their potential applications in industry?
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As far as the lower melting and freezing tendencies of DESs are conecerned, DESs contain large, nonsymmetric ions that have low lattice energy and hence low melting points. They are usually obtained by the complexation of a quaternary ammonium salt with a metal salt or hydrogen bond donor (HBD). The charge delocalization occurring through hydrogen bonding between for example a halide ion and the hydrogen-donor moiety is responsible for the decrease in the melting point of the mixture relative to the melting points of the individual components. I find this article of ACS helpful on this issue: Thanks
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DES (diethylstilbestrol) is a man-made (synthetic) form of estrogen, a female hormone.
Does anyone have any historical data or any physican who may have insight on DES.
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Thank you for your kindness.
Dr. C
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Finds well, but what new you are adding to DES as it is already broken by cryptanalyst in 1977 by using "DES Cracker" machine. so how are you securing
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Good idea!
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Numerical simulation approshes .
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To increase probability of getting an answer to your question, you had better state your question more explicitly. I am afraid nobody will understand what you are asking from those two lines.
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An example hybrid modelling is mixing SD with DES sub-models, where elements in the sub-models communicate and exchange date continuously as the hybrid model is run.
Let us say one has built the SD sub-model using Vensim, and the DES sub-model is built using AnyLogic, what are the ways of making both sub-models to communicate during run time
High Level Architecture approach in combination with Microsoft Excel using Visual Basic for Applications is possible, but this seems to be for periodic and non-frequent communication of the sub-models. So, this approach may be convoluted if used to model a situation where the sub-models need to communicate continuously or in minuscule time steps.
Does anyone have a simplistic approach for modelling the data exchange between sub-models built using different packages?
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Thank you Mohamed-Mourad for the articles sent.
It still seems there is a paucity of research to show how one can model a hybrid data exchange between sub-models that were built using different software pacakges, and for where the data exchange occurs dynamically.
For infrequent data exchange one can use High Level Architecture + Visual Basic for example, and this has been where researchers haved focused their works. But not sure if it can work or how easy it would be for exchange that is dynamically occurring.
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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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Hi,
I am going to simulate a 2D aeroacoustics simulation in Fluent using a DES model on a stator. Actually, the simulation should be performed on a complete 3D rotor-stator setup but due to some limitations, I don’t have access to the rotor geometry and computing power. A simplified model of my setup is shown in the attached picture.
I have been searching for parameters that I can extract from the DES simulations. These are the following parameters that I can think of:
1)A common parameter is the FFT of pressure data recorded in the wake region of the blade. Using FFT, I want to see if I can see tonal noise peaks or broadband peaks. Based on these observations I can characterize the sound sources such as vortex shedding or just random turbulence.
2) Another parameter that I have come across is the sound pressure which can be calculated by subtracting the instantaneous pressure from the average pressure. How this can be done in Fluent, I am not sure.
3) The other is " divergence of velocity" or dilatation contours. I found it in this article
I am not able to understand what's the significance of this parameter.
4) Another quantity that can be visualized is the normalized Q-criterion, but this will be good to see the turbulence sources and not aeroacoustics as such.
5) Also, I was wondering if one can actually extract the noise from a pressure signal at a point so that you can hear it. I came across this in the STAR-CCM+‘s user guide some time ago and they say that it can be done. The guide mentioned that that one needs to perform inverse FFT of the signal.
Perhaps, people with experience in aeroacoustics can suggest me any additional parameters that can be used. Although the near-field region sound is of interest and not far-field, I am open to using the FW-H model if it provides additional insights.
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Dear Ishan Nande,
Here are my suggestions:
1) a 2d simulation of turbulence might be questioned by many people
2) If you extract the pressure signals from the wake this will not be purely noise, but noise+flow. To talk about pure acoustics you need to study it out of the flow, in the far-field.
3) a calculation of the Overall Sound Pressure Level (OASPL) is based on a value of the Root Mean Square (RMS) of pressure fluctuations p'rms [Pa] (referenced to the treshhold of human hearing 2*10^-5 Pa): OASPL dB = 10 log (p'rms^2/p'ref^2) dB. The Sound Pressure Level is a frequency dependent parameter. To get it you need to make a DFFT of p'(t) [Pa] first and transfer the result to the logarithmic scale and get power spectrum of the signal (exact formulas to do that you can get from Matlab examples). As a result you get SPL(f). If you integrate SPL(f) you should get OASPL dB (valuable check).
4) FW-H model is designed for MOVING (e.g. rotating) surfaces in open space...
I hope it was usefull.
Oskar S.
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as choline makes it, betaine should form DES
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Yes, there are examples of DES made with Betaine
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Despite of notable results of decreasing restenosis in patients who have used Drug-eluting stents, There are doubts about impact of DESs on thrombosis and death after one year. Is this been proven as a serious issue or it's ignorable?
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Dear Zahra, there is a major Special Issue in Biomedical Engineering being published in February. You will find this very useful as it presents state of the art and future directions. I am one of the guest editors along with Peter McHugh (Galway, Ireland) and Abdul Barakat (Ecole Polytechnique, Paris)
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S-Boxes in AES and DES effect diffusion in these block cipher systems. I am trying to understand which aspects of these S-boxes attribute to the symmetry of the cipher system.  (i.e. If encryption is in one direction, the decryption is in the reverse direction with the same key.)
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Peter Breuer and Günter Fahrnberger are right. You mix up two terms. Symmetric-key usually means that sender and receiver use the same key for encryption and decryption.
You seem to mean why a symmetric-key cipher is a permutation. This is because each of its operation is maps each input uniquely to one distinct output.
The major purpose of S-boxes is only to some extent the diffusion: more importantly, they are non-linear. Without S-boxes, the DES or the AES could be written as a linear equational system. This would map every plaintext difference between a pair of plaintext P and P' with dP = P xor P' uniquely to a certain ciphertext difference dC = C xor C'. Then, we could take a second pair P'' and P''' with the same difference and predict the difference between their corresponding ciphertexts C'' xor C'''. This would yield a tremendously bad cipher.
The components that are relevant for diffusion are the bit permutation at the end of the DES' round function, and the ShiftRows and MixColumns in the AES.
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Optimal management of patients on NOACs after ACS and PCI with DES. 
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Hi Obiora,
There is good and recent literature on the subject. The evidence for adding aspirin to vitamin K antagonists and clopidogrel is not strong. We have less data with NOACs.
May I suggest you to read Dewilde WJM et al. Triple Therapy for Atrial Fibrillation and Percutaneous Coronary Intervention. A Contemporary Review. JACC 2014; 64 (12), 1270-1280 (September 2014). 
Abstract
Chronic oral anticoagulant therapy is recommended (class I) in patients with mechanical heart valves and in patients with atrial fibrillation with a CHA2DS2-VASc (Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, prior Stroke or transient ischemic attack or thromboembolism, Vascular disease, Age 65 to 74 years, Sex category) score ≥1. When these patients undergo percutaneous coronary intervention with stenting, treatment with aspirin and a P2Y12 receptor inhibitor also becomes indicated. Before 2014, guidelines recommended the use of triple therapy (vitamin K antagonists, aspirin, and clopidogrel) for these patients. However, major bleeding is increasingly recognized as the Achilles' heel of the triple therapy regimen. Lately, various studies have investigated this topic, including a prospective randomized trial, and the evidence for adding aspirin to the regimen of vitamin K antagonists and clopidogrel seems to be weakened. In this group of patients, the challenge is finding the optimal equilibrium to prevent thromboembolic events, such as stent thrombosis and thromboembolic stroke, without increasing bleeding risk.
Best regards,
Thierry