# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=20

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**Page:** 21

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## [Boundary Value Problems in ModelingToolkit](https://discourse.julialang.org/t/boundary-value-problems-in-modelingtoolkit/133491)

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**Author:** [@bradyelster](https://discourse.julialang.org/u/bradyelster)\
**Replies:** 5\
**Last updated:** [November 4, 2025, 6:45pm UTC](https://discourse.julialang.org/t/boundary-value-problems-in-modelingtoolkit/133491 "2025-11-04T18:45:43Z")

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Is it currently possible to symbolically setup and then numerically solve boundary-value problems using ModelingToolkit? This issue tells me this is possible through the dynamic optimization interface but I’m not sure ho…

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## [Q: No SubArray type required for passing partial multidimensional CuArrays?](https://discourse.julialang.org/t/q-no-subarray-type-required-for-passing-partial-multidimensional-cuarrays/133525)

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**Author:** [@Audrius-St](https://discourse.julialang.org/u/Audrius-St)\
**Replies:** 4\
**Last updated:** [November 4, 2025, 6:31pm UTC](https://discourse.julialang.org/t/q-no-subarray-type-required-for-passing-partial-multidimensional-cuarrays/133525 "2025-11-04T18:31:48Z")

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Hello, To pass part of a multidimensional array in Julia on the CPU on has to use the SubArray type in the function arguments. This does not seem to be the case for Julia on the GPU. Excerpted from the MWE below: …

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## [Computing Hessian of the Langrangian efficiently with DI.jl](https://discourse.julialang.org/t/computing-hessian-of-the-langrangian-efficiently-with-di-jl/133462)

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**Author:** [@franckgaga](https://discourse.julialang.org/u/franckgaga)\
**Replies:** 15\
**Last updated:** [November 4, 2025, 5:16pm UTC](https://discourse.julialang.org/t/computing-hessian-of-the-langrangian-efficiently-with-di-jl/133462 "2025-11-04T17:16:42Z")

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Hello, The new MOI.VectorNonlinearOracle support providing the Hessian of the Langrangian function, defined as, according to MOI.jl doc: \\sum\_i \\mu\_i \\nabla^2 f\_i(\\mathbf{x}) but the Langrangian typically also includ…

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## [Minimization of degenerate eigenvalue of sparse matrix](https://discourse.julialang.org/t/minimization-of-degenerate-eigenvalue-of-sparse-matrix/133615)

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**Author:** [@mxhbl](https://discourse.julialang.org/u/mxhbl)\
**Replies:** 12\
**Last updated:** [November 4, 2025, 4:30pm UTC](https://discourse.julialang.org/t/minimization-of-degenerate-eigenvalue-of-sparse-matrix/133615 "2025-11-04T16:30:17Z")

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Hi, I have a tricky optimization problem where I need to minimize a specific eigenvalue of a matrix M(\\theta) that depends continuously on a set of parameters \\theta. The problem is that the eigenvalue is usually degene…

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## [Difficulty using Submodels in Turing](https://discourse.julialang.org/t/difficulty-using-submodels-in-turing/133634)

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**Author:** [@slwu89](https://discourse.julialang.org/u/slwu89)\
**Replies:** 4\
**Last updated:** [November 4, 2025, 2:48pm UTC](https://discourse.julialang.org/t/difficulty-using-submodels-in-turing/133634 "2025-11-04T14:48:33Z")

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Hi, I am trying to use Submodels as described in Submodels – Turing.jl. However I cannot figure out how to get it to work. I posted a deliberately simplified reproducable example below, and the error I was getting below …

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## [Can't get the example dualization to work](https://discourse.julialang.org/t/cant-get-the-example-dualization-to-work/129478)

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**Author:** [@brandon-lee-17](https://discourse.julialang.org/u/brandon-lee-17)\
**Replies:** 5\
**Last updated:** [November 4, 2025, 7:07am UTC](https://discourse.julialang.org/t/cant-get-the-example-dualization-to-work/129478 "2025-11-04T07:07:27Z")

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I can’t seem to get the first motivating example in Dualization.jl to work (at https://jump.dev/Dualization.jl/dev/examples/) using JuMP, Dualization model = Model() @variable(model, x) @variable(model, y) @variable(mod…

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## [Efficient lookup of UInt indices in large GPU arrays](https://discourse.julialang.org/t/efficient-lookup-of-uint-indices-in-large-gpu-arrays/133630)

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**Author:** [@Gattu\_Mytraya](https://discourse.julialang.org/u/Gattu_Mytraya)\
**Replies:** 0\
**Last updated:** [November 3, 2025, 9:09pm UTC](https://discourse.julialang.org/t/efficient-lookup-of-uint-indices-in-large-gpu-arrays/133630 "2025-11-03T21:09:23Z")

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Hi all, I have a GPU kernel where the main bottleneck is finding the index of an unsigned integer in a large constant array (lll\_basis in the code below). Typical array sizes are around \\sim 10^7, but I am hoping to wo…

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## [Electrostatics in Julia](https://discourse.julialang.org/t/electrostatics-in-julia/41633)

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**Author:** [@jarvist](https://discourse.julialang.org/u/jarvist)\
**Replies:** 32\
**Last updated:** [November 3, 2025, 5:38pm UTC](https://discourse.julialang.org/t/electrostatics-in-julia/41633 "2025-11-03T17:38:40Z")

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Does anyone know of Julia libraries implementing electrostatic summations in Julia? (e.g. Ewald, Particle Mesh Ewald, Fast Multipole Method…) I haven’t been able to find much by googling: A fairly complex bio orienta…

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## [Molly.jl - trying to understand di-atomic example](https://discourse.julialang.org/t/molly-jl-trying-to-understand-di-atomic-example/133430)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 19\
**Last updated:** [November 2, 2025, 5:41pm UTC](https://discourse.julialang.org/t/molly-jl-trying-to-understand-di-atomic-example/133430 "2025-11-02T17:41:47Z")

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Thanks for lots of help on previous Molly.jl questions. I’m trying to understand the " Simulating diatomic molecules example. I have re-structured the example to attempt to figure out the key ideas. See below (I skipped…

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## [Modelling collisions of agents with the environment in discrete time](https://discourse.julialang.org/t/modelling-collisions-of-agents-with-the-environment-in-discrete-time/133229)

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**Author:** [@simonsteiger](https://discourse.julialang.org/u/simonsteiger)\
**Replies:** 1\
**Last updated:** [November 2, 2025, 2:00pm UTC](https://discourse.julialang.org/t/modelling-collisions-of-agents-with-the-environment-in-discrete-time/133229 "2025-11-02T14:00:09Z")

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Hi everyone, I am new to agent-based modelling and have recently started using Agents.jl for a research project. Thanks a lot for this great package! The model should simulate how (for example) coconuts disperse throug…

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## [Lux/Enzyme error when Training my model?](https://discourse.julialang.org/t/lux-enzyme-error-when-training-my-model/133442)

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**Author:** [@rkube](https://discourse.julialang.org/u/rkube)\
**Replies:** 9\
**Last updated:** [November 2, 2025, 1:44am UTC](https://discourse.julialang.org/t/lux-enzyme-error-when-training-my-model/133442 "2025-11-02T01:44:19Z")

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Hi, I’m trying to get a simple language model to train using Lux/Enzyme and get a big scary error. Does anyone have insight into how to get to the bottom of this? Is there an error in the MWE? I tried Zygote and it run…

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## [Side effects (or intended effects) in TidierData?](https://discourse.julialang.org/t/side-effects-or-intended-effects-in-tidierdata/133438)

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**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 11\
**Last updated:** [October 31, 2025, 10:53pm UTC](https://discourse.julialang.org/t/side-effects-or-intended-effects-in-tidierdata/133438 "2025-10-31T22:53:35Z")

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julia\> df4 = DataFrame(x = \["a", "b", "a", "b", "C", "a"\], y = 1:6, yz = 13:18, a = \[join(rand('a':'z',4)) for \_ in 1:6\], ab = 12:-1:7) 6×5 DataFrame Row │ x y yz a ab │ String Int64 Int6…

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## [Solving Projection onto Linear Equality for Multiple Input Vectors](https://discourse.julialang.org/t/solving-projection-onto-linear-equality-for-multiple-input-vectors/133428)

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**Author:** [@RoyiAvital](https://discourse.julialang.org/u/RoyiAvital)\
**Replies:** 11\
**Last updated:** [October 31, 2025, 8:52pm UTC](https://discourse.julialang.org/t/solving-projection-onto-linear-equality-for-multiple-input-vectors/133428 "2025-10-31T20:52:18Z")

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I am after solving the projection onto a Linear Equation problem: \\arg \\min\_{\\boldsymbol{x}} \\frac{1}{2} {\\left\\| \\boldsymbol{x} - \\boldsymbol{y} \\right\\|}\_{2}^{2} \\; \\text{ subject to } \\boldsymbol{A} \\boldsymbol{x} =…

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## [Examples of dynamical physical systems with exogenous inputs described by UDEs](https://discourse.julialang.org/t/examples-of-dynamical-physical-systems-with-exogenous-inputs-described-by-udes/133373)

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**Author:** [@Emil\_Martinsen](https://discourse.julialang.org/u/Emil_Martinsen)\
**Replies:** 4\
**Last updated:** [October 31, 2025, 12:55pm UTC](https://discourse.julialang.org/t/examples-of-dynamical-physical-systems-with-exogenous-inputs-described-by-udes/133373 "2025-10-31T12:55:21Z")

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Can anyone point me to some good examples (code, papers, tutorials) of a dynamical physical system that are modelled with UDEs, i.e., ODEs where parts are known and other parts are unknown and modelled by a neural networ…

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## [AD of UDEs - how to set it up?](https://discourse.julialang.org/t/ad-of-udes-how-to-set-it-up/133461)

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**Author:** [@Emil\_Martinsen](https://discourse.julialang.org/u/Emil_Martinsen)\
**Replies:** 13\
**Last updated:** [October 31, 2025, 7:13am UTC](https://discourse.julialang.org/t/ad-of-udes-how-to-set-it-up/133461 "2025-10-31T07:13:44Z")

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Hi! Im new to Julia and SciML but I am really curious to see how combining ODE’s with neural network could improve the predictive performance of the model we are developing for solvent-based CO2 capture. My current setu…

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## [Lumped beam model](https://discourse.julialang.org/t/lumped-beam-model/128512)

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**Author:** [@yjr](https://discourse.julialang.org/u/yjr)\
**Replies:** 8\
**Last updated:** [October 30, 2025, 10:52pm UTC](https://discourse.julialang.org/t/lumped-beam-model/128512 "2025-10-30T22:52:45Z")

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Hello, I’m trying to implement a 2D lumped beam model with modelingtoolkit. Using the small angle approximation, I managed to have something working with 5 elements. But increasing the number of elements to 6 make ODEPr…

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## [How to extract location from Strided GeoTIFF raster?](https://discourse.julialang.org/t/how-to-extract-location-from-strided-geotiff-raster/124973)

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**Author:** [@cshen](https://discourse.julialang.org/u/cshen)\
**Replies:** 14\
**Last updated:** [October 30, 2025, 4:32pm UTC](https://discourse.julialang.org/t/how-to-extract-location-from-strided-geotiff-raster/124973 "2025-10-30T16:32:44Z")

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Hello, I’ve been trying to read some geotiff datasets. Reading it with GeoTIFF.jl results in a GeoTIFF.GeoTIFFImageIterator{TiffImages.StridedTaggedImage{...}}}. This case is not really documented anywhere neither in G…

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## [Robust solver for ℝ³ → ℝ³ root with flat parts](https://discourse.julialang.org/t/robust-solver-for-root-with-flat-parts/133481)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 5\
**Last updated:** [October 30, 2025, 2:40pm UTC](https://discourse.julialang.org/t/robust-solver-for-root-with-flat-parts/133481 "2025-10-30T14:40:21Z")

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I have an ℝ³ → ℝ³ function f which is differentiable (the computation uses an implicit solution, but I implemented the derivatives for Enzyme.jl, Mooncake.jl, and ForwardDiff.jl). I would like to find the root f(x) = 0. …

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## [CSV.jl "corrupts" data when a field is very large](https://discourse.julialang.org/t/csv-jl-corrupts-data-when-a-field-is-very-large/133513)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [October 30, 2025, 1:06pm UTC](https://discourse.julialang.org/t/csv-jl-corrupts-data-when-a-field-is-very-large/133513 "2025-10-30T13:06:08Z")

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I have a CSV (from here) where one field is a MULTIPOLYGON that can be very large, and when I import it with CSV (even a smaller 10 rows version) I got a strange corruption: julia\> data = CSV.read("MYRIAD-HES/test.cs…

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## [Memory issues for long SSA simulations with mass action jumps](https://discourse.julialang.org/t/memory-issues-for-long-ssa-simulations-with-mass-action-jumps/133530)

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**Author:** [@jworsfold](https://discourse.julialang.org/u/jworsfold)\
**Replies:** 1\
**Last updated:** [October 30, 2025, 10:53am UTC](https://discourse.julialang.org/t/memory-issues-for-long-ssa-simulations-with-mass-action-jumps/133530 "2025-10-30T10:53:39Z")

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I’m trying to find the stationary distribution of a Master Equation where the state space is bounded but can be too large to solve using FiniteStateProjection.jl so I’m left with running Gillespie simulations. Running l…

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## [Issue: Enzyme + Flux double differentiation on custom layer](https://discourse.julialang.org/t/issue-enzyme-flux-double-differentiation-on-custom-layer/133503)

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**Author:** [@Gianmarco](https://discourse.julialang.org/u/Gianmarco)\
**Replies:** 3\
**Last updated:** [October 30, 2025, 1:52am UTC](https://discourse.julialang.org/t/issue-enzyme-flux-double-differentiation-on-custom-layer/133503 "2025-10-30T01:52:28Z")

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Hi, I’m using Flux and Enzyme for a project, and the entire architecture is built on top of these two libraries. So unless strictly necessary, I’d like to stay within the Flux/Enzyme ecosystem. For both libraries i’m u…

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## [Area interpolation between Shapefile (country borders) and WKT (multi)polygon elements in a CSV file](https://discourse.julialang.org/t/area-interpolation-between-shapefile-country-borders-and-wkt-multi-polygon-elements-in-a-csv-file/133458)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 15\
**Last updated:** [October 30, 2025, 1:01am UTC](https://discourse.julialang.org/t/area-interpolation-between-shapefile-country-borders-and-wkt-multi-polygon-elements-in-a-csv-file/133458 "2025-10-30T01:01:00Z")

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I have a shapefile of administrative country borders and a CSV file where one field is “geometry” and embed polygon and multipolygon data as "Well Known Text (WKT). Both are in EPSG:4326. How can I retrieve for each ele…

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## [New "easy rule" system for Enzyme](https://discourse.julialang.org/t/new-easy-rule-system-for-enzyme/133522)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 4\
**Last updated:** [October 29, 2025, 9:27pm UTC](https://discourse.julialang.org/t/new-easy-rule-system-for-enzyme/133522 "2025-10-29T21:27:57Z")

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Hi there @wsmoses and friends, Thanks for the new easy rule system! Making rules more accessible is a great idea to get more people into autodiff (that’s how I got hooked in the first place). I’m curious to understand …

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## [ModelingToolkit Symbolics maxiters not enough](https://discourse.julialang.org/t/modelingtoolkit-symbolics-maxiters-not-enough/133463)

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**Author:** [@AlirezaMiraliakbar](https://discourse.julialang.org/u/AlirezaMiraliakbar)\
**Replies:** 2\
**Last updated:** [October 28, 2025, 7:08pm UTC](https://discourse.julialang.org/t/modelingtoolkit-symbolics-maxiters-not-enough/133463 "2025-10-28T19:08:48Z")

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Hi, I am trying to model a chemical process with modeling toolkit and I have set 4 of my variables to irreducible = true. However, with doing this, I get the warning message from Symbolics that: Warning: Did not converg…

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## [Automatic symbolic function barrier generation](https://discourse.julialang.org/t/automatic-symbolic-function-barrier-generation/133487)

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**Author:** [@sablonl](https://discourse.julialang.org/u/sablonl)\
**Replies:** 0\
**Last updated:** [October 28, 2025, 4:00pm UTC](https://discourse.julialang.org/t/automatic-symbolic-function-barrier-generation/133487 "2025-10-28T16:00:10Z")

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Hi, I’m working with ModelingToolkit.jl and I have an issue with complex symbolic expressions, on which mtkcompile takes a lot of time. I discovered that I can hide expressions behind a function barrier using @register…

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## [Molly.jl - Shear Viscosity Notebook - Questions](https://discourse.julialang.org/t/molly-jl-shear-viscosity-notebook-questions/133466)

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**Author:** [@ziolai](https://discourse.julialang.org/u/ziolai)\
**Replies:** 2\
**Last updated:** [October 28, 2025, 11:35am UTC](https://discourse.julialang.org/t/molly-jl-shear-viscosity-notebook-questions/133466 "2025-10-28T11:35:09Z")

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This post concerns the tutorial at SINEQ Shear Viscosity. Q1: To what extend is the result obtained for the shear viscosity independent of the number of particles in the simulation? Q2: What happens in case that the nu…

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## [Help replacing \`LScene\` by \`Axis3\`](https://discourse.julialang.org/t/help-replacing-lscene-by-axis3/133467)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 1\
**Last updated:** [October 27, 2025, 7:32pm UTC](https://discourse.julialang.org/t/help-replacing-lscene-by-axis3/133467 "2025-10-27T19:32:23Z")

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Consider a 100x100x50 grid in LScene: This is how it looks in Axis3(viewmode=:free, aspect=:data): It is somewhat “squeezed” compared to the previous visualization. Is there a way to reproduce the same perspecti…

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## [Makie recipes on a Errorline like plot](https://discourse.julialang.org/t/makie-recipes-on-a-errorline-like-plot/133456)

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**Author:** [@dmetivie](https://discourse.julialang.org/u/dmetivie)\
**Replies:** 2\
**Last updated:** [October 27, 2025, 5:31pm UTC](https://discourse.julialang.org/t/makie-recipes-on-a-errorline-like-plot/133456 "2025-10-27T17:31:50Z")

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Using the new Makie 0.24 recipe system, I want to create the StatsPlots.jl recipe for errorline (see original definition). Here is a simplified version of the plume errorline. This might be very simple but could not fi…

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## [How to couple different wind farm models?](https://discourse.julialang.org/t/how-to-couple-different-wind-farm-models/133464)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 0\
**Last updated:** [October 27, 2025, 5:08pm UTC](https://discourse.julialang.org/t/how-to-couple-different-wind-farm-models/133464 "2025-10-27T17:08:10Z")

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We are brainstorming how to best couple different scale models, e.g., fast small-scale models with meso-scale models, for example, Floridyn.jl with a Julia version of TFSO-software / WAYVE · GitLab . I guess both models…

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## [Robust resampling/interpolation method](https://discourse.julialang.org/t/robust-resampling-interpolation-method/132665)

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**Author:** [@langestefan](https://discourse.julialang.org/u/langestefan)\
**Replies:** 25\
**Last updated:** [October 27, 2025, 1:15pm UTC](https://discourse.julialang.org/t/robust-resampling-interpolation-method/132665 "2025-10-27T13:15:54Z")

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I am working on a system identification problem with poor quality input data. The data describes a heating system, with thermostat temperatures, thermal power inputs, supply/return water temperatures etc. Some issues w…

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