# COMSOL Blog

## Using the Previous Solution Operator in Transient Modeling

##### Walter Frei | June 25, 2015

COMSOL Multiphysics version 5.1 includes a Previous Solution operator within time-dependent studies. This operator allows you to evaluate quantities at the previous time step when using the default implicit time-stepping algorithm. Let us take a look at how this operator is implemented and then examine how it can be used for various modeling needs.

### Modeling Laser-Material Interactions in COMSOL Multiphysics

##### Walter Frei | June 22, 2015

A question that we are asked all of the time is if COMSOL Multiphysics can model laser-material interactions and heating. The answer, of course, depends on exactly what type of problem you want to solve, as different modeling techniques are appropriate for different problems. Today, we will discuss various approaches for simulating the heating of materials illuminated by laser light.

### Useful Tools for Postprocessing in COMSOL Multiphysics

##### Lexi Carver | June 8, 2015

In recent posts, we have covered a variety of plot types used for postprocessing simulation results in COMSOL Multiphysics and the ways that they can help you understand and share your results. Now let’s take a look at some tricks to simplify work in the graphics window.

### Using Deformations to Visualize Physical Motion

##### Lexi Carver | April 28, 2015

When simulating acoustic waves, vibrating mechanical hardware, or fluid in a channel — just to name a few applications — you may be interested in visualizing the movement or shape change in a device. Postprocessing and visualization can help enhance your understanding of simulation results, and using plots to illustrate physical motion allows you to put everything into perspective. Deformations are a great way to accomplish this.

### Implementing the Weak Form with a COMSOL® App

##### Chien Liu | April 16, 2015

Previously in our weak form series, we discretized the weak form equation to obtain a matrix equation to solve for the unknown coefficients in our simple example problem. Following the same procedure as in this previous blog post, we will implement the equation in the COMSOL Multiphysics® software with additional steps included to examine the matrices. We will find it more convenient to use a COMSOL® software application to display all relevant matrices at once, arranged logically on one screen.

### Modeling Laser-Material Interactions with the Beer-Lambert Law

##### Walter Frei | April 13, 2015

High-intensity lasers incident upon a material that is partially transparent will deposit power into the material itself. If the absorption of the incident light can be described by the Beer-Lambert law, it is possible to model this power deposition using the core functionality of COMSOL Multiphysics. We will demonstrate how to model the absorption of the laser light and the resultant heating for a material with temperature-dependent absorptivity.

### Can We Hear the Shape of a Drum?

##### Chien Liu | April 1, 2015

Over half a century ago, Mark Kac gave an interesting lecture on a question that he had heard from Professor Bochner ten years earlier: “Can one hear the shape of a drum?” He focused on the (then undetermined) uniqueness of the set of eigenvalues given the shape of a vibrating membrane. The eigenvalue problem has since been solved and here we explore the “hearing” part of the question by considering some interesting physical effects.

### Improving Your Meshing with Partitioning

##### Walter Frei | March 27, 2015

Often, the most tedious step of finite element modeling is subdividing your CAD geometry into a finite element mesh. This step, usually just called meshing, can sometimes be fully automated. More often, however, the careful finite element analyst will want to semi-manually create their meshes. Although this does require more work, sometimes there are significant advantages in doing so. In this blog entry, we will look at one of the key manual meshing techniques: the concept of geometric partitioning.

### Curve Fitting of Experimental Data with COMSOL Multiphysics

##### Walter Frei | March 19, 2015

We often need to work with experimental data in COMSOL Multiphysics, usually to represent material properties or other inputs to our model. However, experimental data is often noisy; it contains experimental errors that we do not want to introduce into our simulations. In this blog post, we will look at how to fit smooth curves and surfaces to experimental data using the core functionality of COMSOL Multiphysics.

### Running COMSOL Multiphysics® with Amazon EC2™

##### Pär Persson Mattsson | February 20, 2015

We have previously written about HPC with the COMSOL Multiphysics® software, clusters, and hybrid computing. But not all of us have a cluster available in the office (or the hardware to build a Beowulf cluster). So what possibilities do we have if we really need that extra compute power that a cluster can give us? One solution is to utilize cloud computing, a service that provides compute power on a temporary basis, to give our computations and productivity a boost.

### Implementing a Thermostat with the Events Interface

##### Walter Frei | February 19, 2015

A thermostat is a device that senses the temperature of a system and uses this information to control the system’s heaters, or coolers, to keep the temperature close to a desired setpoint. While there are many different types of thermostats, we will focus today on one that turns a heater either on or off based upon two setpoints. This is known as an on-off or a bang-bang controller, and it can be implemented with the Events interface in COMSOL Multiphysics.