update README.md.

Signed-off-by: 刘明宏 <liuminghong@mail.sdu.edu.cn>

README.md

@@ -2,7 +2,9 @@
 
 #### Introduction
 em3d-MT is an open-source MATLAB-based package for 3D forward modeling of magnetotelluric (MT) and radiomagnetotelluric (RMT) data. It is built on an edge-based finite element (FE) framework and solves the full-wave Maxwell’s equations, accounting for both conduction and displacement currents. This enables accurate modeling in the RMT frequency range.
+
 The software supports arbitrary anisotropy in both electrical conductivity and dielectric permittivity, allowing flexible simulation of complex geological scenarios. It utilizes unstructured tetrahedral meshes and a customizable geological modeling workflow to accommodate irregular terrain and heterogeneous media.
+
 To address the high computational cost of 3D modeling, em3d-MT integrates a direct linear solver with a double-layer parallelization strategy. This design supports efficient simulation over multiple frequencies using OpenMP-based multithreading and frequency-level parallelization.
 
 #### software framework
@@ -16,12 +18,14 @@ MATLAB (R2023a or later): The core environment in which em3d-MT operates.
 
 em3d-MT relies on several external tools and libraries to facilitate 3D geological modeling and mesh generation. The following software is required for proper functionality:
 
-GeoMesh
+GeoMesh：
+
 For 3D geological modeling and mesh generation, GeoMesh is used. This is an open-source tool specifically designed for electromagnetic (EM) modeling, based on the COMSOL Multiphysics and MATLAB interface (Liu et al., 2024). GeoMesh generates unstructured tetrahedral meshes, which are ideal for representing complex subsurface structures in the forward modeling process. You can find the tool at https://gitee.com/sduem/geomesh
 
 Additionally, em3d-MT supports two types of direct solvers for solving the finite element system:
 
 Panua-Pardiso:
+
 An optimized direct solver used for solving large sparse linear systems. It offers high performance and memory efficiency. More information can be found at https://panua.ch/pardiso/
 
 UMFPACK: