Simpeg

- from pr 687
- commits from: micmitch, lheagy
- review from: lheagy

Summary
Fixed the way E fields were being computed in the fields object for the DC_CC problem. Added tests the check E and J for a electric dipole in a fullspace against the analytic solutions. Still lacking a test for charges.

- from PR: 685
- commits from lheagy
- review from thast

Bug fix for the way that we set the `_nC_residual` in the Regularization; this is important for constructing a default `W` matrix used inside the norm. We also clean up the logic of how we set nC_residual and adds a test to ensure it doesn't break in the future.

Core code for VRM problem

Here, we add the core functionality for using potential fields to model viscous remanent magnetic responses. The approach has been adapted from the thesis "Forward modeling and inversion of viscous remanent magnetization responses in the time domain" (Cowan, 2016).

Details

* from pr 645
* commits from dccowan
* review from lheagy

Highlights

* Model VRM responses on 3D tensor and 3D tree meshes
* Model VRM responses for a large variety of current waveforms
* Model VRM responses for a multitude of transmitter types
* Invert the response to recover a representative physical property for VRM

Future work

* Provide adequate documentation
* Provide working examples with figures
* Provide workflow for removing VRM response from TEM data

Example


- from pr 682
- commits from lheagy, review from sgkang

New Map: ParametricBlock
- add a parametric block map (2D and 3D) (eg. as shown in https://github.com/simpeg-research/heagy_2018_AEM/blob/master/Heagy_etal_2018_aem_workshop.pdf)


Renamed maps
- rename Parametrized maps to Parametric maps
- update examples to be consistent with this

- from PR 677
- commits from lheagy
- review from sgkang, rowanc1

tl; dr
- inductive source bug fix for permeable targets
- solve the magnetostatic problem for inductive sources that have initial fields
- new waveforms: trapezoid, quarter-sine ramp on

Bug Fix: TDEM Inductive sources + permeable targets
How we initially calculated the source term for inductive sources when the model includes permeability was incorrect (I found this by comparing a magnetostatic solution with a late on-time solution. The late on-time solution matched the case where no permeable material was included), this pr fixes that for the E-B formulation.

In addition, we now have the option to solve the magnetostatic problem for initial fields when permeable material is included, so a shut-off waveform can be used when permeable materials are in the domain

There is now a test to ensure that inductive sources are treating permeability properly

New Waveforms
- `TrapezoidWaveform` and `QuarterSineRampOnWaveform`

python
offTime=10
quarter_sine = TDEM.Src.QuarterSineRampOnWaveform(ramp_on=np.r_[0., 3], ramp_off=offTime - np.r_[1., 0] )
trapezoid = TDEM.Src.TrapezoidWaveform(ramp_on=np.r_[0., 3], ramp_off=offTime - np.r_[1., 0] )

nT = 1000
time = 10.*np.arange(nT)/nT
quarter_sine_plt = np.r_[[quarter_sine.eval(t) for t in time]]
trapezoid_plt = np.r_[[trapezoid.eval(t) for t in time]]


fig, ax = plt.subplots(1, 2, figsize=(8, 4))
ax[0].plot(time, quarter_sine_plt)
ax[0].set_title('quarter sine waveform')

ax[1].plot(time, trapezoid_plt)
ax[1].set_title('trapezoid waveform')

plt.tight_layout()



NSEM upgrades
Collections of updates focused on improved NSEM data functionality and updating `NSEM` module to comply with new developments.
- from pr 515
- commits from grosenkj
- review from rowanc1, lheagy

Highlights
- Compliance with new `SimPEG` features
- Uses the `SimPEG` new objective functions
- Relying on other latest and greatest `SimPEG` developments.
- Addresses some of the long-term development goals in 452
- Better plotting
- Name space clean ups
- `NSEMdata` improvements
- Adds `standarad_devation`, `floor` and `calc_uncertainies` to `Data` that are indexable in the same way as the data (in parallel with 672 and 202)
- Adds functions to work and manipulate `NSEMData` in `Utils.dataUtils`
- Plotting methods for `Data`
- New interactive `NSEMDataViewer` for comparing data
- Improved example
- 1D forward and inversion
- 3D foward modelling


- pep8 cleaning and maintainance and adding documentation.
- Address issues 631 and 665

Backward compatibility
From the current `master` version of `NSEM` module, there isn't a large difference and backward compatibility should be intact.
Majority of the work in this PR is focused on adding utilities to work and interact with `NSEM` data, clarifying how to use the code with better examples and do some minor maintenance.