Add BEM to docs

Author: gavinmacaulay

docs/usage.md

@@ -31,6 +31,7 @@ The following models are available in echoSMs:
 
 |Model type|Python class name(s)|Description|
 |----------|----------|-----------|
+|Boundary element method|BEMModel|Arbitrary shapes. The current implementation only does pressure release surfaces and has spurious results at internal resonance frequencies and does not include the CHIEF technique to avoid these)|
 |Deformed cylinder|DCMModel|Truncated cylinders with various boundary conditions|
 |Distorted-wave Born approximation|DWBAModel|Weakly scattering objects with piecewise circular cross-sections and homogenous interiors with an optional stochastic variant (the SDWBA)|
 |Elastic sphere|ESModel|Elastic spheres, such as echosounder calibration spheres|

src/echosms/bemmodel.py

@@ -72,8 +72,8 @@ def calculate_ts_single(self, medium_c: float, theta: float, phi: float,
         Notes
         -----
         This models implements the classical BEM for pressure release targets
-        using `scipy.linalg.solve` with k/4 diagonal regularization. The cod was
-        kindly provided by Marek Moszyński.
+        using with k/4 diagonal regularization. The code
+        was kindly provided by Marek Moszyński.
         """
 
         # Note: th, ph - incident wave direction angles in radians