A few points that might be of general interest:

1. The dates: The date of Huygens' first written down material, which was orally presented to the French Academy of Sciences, is 1678---in contrast to the oft-quoted date of 1690. 1690 was the year of the first, French, publication of these notes (plus other material) in the form of a book.

Hi all,

1. In the past, we have had quite some discussion regarding both open-access and open-access journals. However the slant in this blog post is different. I am not concerned here much about open-access journals per say.

Here, I am concerned about the policies that the prominent commercial journals keep regarding posting preprints on the Internet before these articles are submitted to them. I would like to know about policies kept in this regard by the commercial journals in the fields of physics, mechanics, and engineering (including software engineering, computational science and engineering, etc.).

Equations are of central importance in all of science and engineering, but especially so in mechanics.

Even leaving aside algebraic equations, handbooks on PDEs alone list hundreds of equations. However, a few of these do stand out, either because they encapsulate some fundamental aspect of physics/science/engg., or because they serve as simpler prototypes for more complex situtations, or simply because they are so complex as to be fascinating by themselves. There might be other considerations too... But the fact is, some equations really do stand out as compared to others.

Hi all,

Just thought that the following paper archived at the arXiv yesterday could be of general interest to any mechanician:

Xingyu Zhang, Matthew Tomes, Tal Carmon (2011) "Precession optomechanics," arXiv:1104.4839 [^]

The fig. 1 in it makes the matter conceptually so simple that the paper can be recommended to any mechanician for his general reading, and not only to a specialist in the field.

--Ajit

[E&OE]

Hi all,

1. A new version of Eigen (v 3.0 now) is out (on March 23, 2011), and it seems promising. First, a few links:

The main page for the project is here: [^]. The page for v.3.0 is here: [^]. It seems to be very fast: [^].

2. No compilation issues on the Win32 platform: I just downloaded it today, and found that it compiles OK with VC++ 10.0 on Win32 (the BUILD_ALL project). I haven't had the time to try anything further, though.

Can you define FEM in one line?

If yes, what would it be? And, in that case, permit me a second question: How?

...Really interested in knowing what the members of this community think (of this matter), if they do...

--Ajit

[E&OE]

Here is an idea I submit for consideration by all iMechanicians, but esp. so by the admins and moderators. Discussion is welcome.

Idea: Why not have a Mechanics Gallery section here?

Origin: Recently, I was browsing for some OpenGL-encapsulating C++ class libraries, e.g. OpenSceneGraph, VTK, the game development libraries, etc. The Web sites of all such libraries always carry a "Gallery" page which is designed to attract the potential users. The Gallery page shows the capabilities and advantages of that library/framework.

A similar idea is possible for our field too. 

Hi all, 

[Warning: The writing is long, as is usually the case with my posts :)]

It all began with a paper that I proposed for an upcoming conference in India. The extended abstract got accepted, of course, but my work is still in progress, and today I am not sure if I can meet the deadline. So, I may perhaps withdraw it, and then submit a longer version of it to a journal, later.

As a consultant in computational mechanics, I currently help write some FEM-related code, and while doing this job, an episode from a recent past came to my mind. Let me go right on to the technical issue, keeping aside the (not so good) particulars of that episode. (In case you are curious: it happened outside of my current job, during a job interview.)

If you are a design engineer, FE analyst, researcher, or any professional dealing with stress analysis in your work, I seek answers to a couple of questions from you:

Question 1:

A recent discussion at iMechanica following my last post here [^] leads to this post. The context of that discussion is assumed here.

I present here three sample problems, thought of almost at random, just to see how the suggestions made by Jaydeep in the above post work out.

To the best of my knowledge, the two momentum conservation principles, namely, the conservation of linear- and angular-momentum, operate completely independent of each other. For an isolated object, there is no possibility of conversion of one form of momentum to the other.

Today, when I Googled on this topic, I found that most pages agree with my position above. Yet, to my great surprise, I did run into a page written by an engineer here [^] claiming that the linear momentum is only a special case of the angular momentum... Here is the relevant excerpt (bold emphasis mine):

Summary:

I am thinking of informally conducting a specific case-study concerning the FEA solvers. The reference problem is a very simple but typical problem from stress analysis, leading of course to the linear systems: Ax = b and Ax = Lx.

I seek advice as to what software libraries currently available in the public domain would be best to use---the ones that would be fastest in terms of execution time for the reference problem.

I have a personal and longer-term research interest with certain issues related to the solvers technologies.

Suggestions and comments are welcome!

(1.) The Reference Problem:

Dear iMechanicians,

I have applied for the job of "Associate Professor" in the Department of Mechanical Engineering at COEP, Pune, India [^]---the same place from where I did my PhD (Mech.) research.

I most earnestly make an appeal to you to provide me with an informal support for my job application by way of a brief email recommendation. My resume may be found here [^].

Since my research touches on the basics of QM, I have developed this habit of visiting arXiv.org every now and then. Last week or so, at arXiv.org, I found a couple of interesting articles on physics in general. I would like to share these with you.

I am pleased to inform you that I will be defending my Ph.D. thesis, formally in mechanical engineering, at COEP, University of Pune, India, on the next Sunday (i.e. 20th September, 2009).

The title of my thesis is: "A New Approach to Computer Modeling and Analysis of Certain Fundamental Field Problems from Engineering Sciences." 

I am attaching the 10 (actually 13) pages long abstract of my thesis for your information. The thesis is based on my published articles which may be downloaded from my Web site [here].

Unlike other blog-posts of mine, I am not going "own" this particular thread. By that, I mean to say: I am going to only begin this thread and immediately turn it over to you completely. I am not going to watch over whether the discussion here continues to stick to its main theme or not, whether it slides into some minor side issues, whether it deserts the main theme altogether, etc., the way I usually do.

- - - - -

This thread is meant to be about the following book:
 
Carol White , "Energy Potential: Toward a New Electromagnetic Field Theory," (with essays by Bernhard Riemann trans. from German by J. J. Cleary, Jr.), Campaigner Publications, New York, 1977.

If someone knows of books/articles dealing with the meaning of the concept of potential in physics (or concerning the physical bases underlying the energy methods of mechanics) then I would very much appreciate getting to know about these.

0. I was idly thinking about the current H1N1 flue pandemic, and the following things occurred to me. Please note, I know very little about this subject matter. So, please consider descriptions in the following as, at best, tentative.

1. There is a basic difference between how alcohol kills viruses and how salt-water kills bacteria. [Alcohol is used in the hand-cleaners they use in hospitals. Girgling with salt-water is the first line of defense (and an unexpectedly highly effective one) which is well known for millenia.]

But the mechanisms involved are different.

(i) 3rd International Congress on Computational Mechanics and Simulation (ICCMS09) to be held this year at IIT Bombay, on December 1--5, 2009. Abstracts due by July 31, 2009:

http://www.civil.iitb.ac.in/help/114_iccms09/iccms09.html

(ii) 54th Congress of the Indian Society of Theoretical and Applied Mechanics (An International Meet), to be held this year at the Netaji Subhas Institute of Technology, New Delhi, during December 18--21, 2009. Abstracts due by September 30, 2009:

http://www.webmath.iitkgp.ernet.in/~istam/

http://www.nsit.ac.in

Ideally, this post of mine should carry a poll, but I guess as an ordinary user, I cannot insert one.

Currently, I am writing a small software program that is especially designed to help learn FEM. For instance, I will be providing detailed listings for every intermediate step, e.g. all those [D], [B], [k], etc. matrices for each element, as well as the final assembled global system {F} = [K]{d} and its solution separately at each Gauss point. Only linear static problems for the time being; will add transients/eigenvalue problems in near future.

Needless to add, to make it all easy to use, I am providing a GUI as well.

The following is a (relatively minor) question which had occurred to me more than two decades ago. By now I have forgotten precisely when it was... It could have been when I was in my TE (third year engineering) at COEP. ... Or, perhaps, it was later on, when I as at IIT Madras (studying stress analysis on my own). ... I don't remember precisely when it occurred to me, only *how* it did---it was when I was poring over the first part of Dieter's book.

IMHO, a matter like this should have been explicitly dealt with by the undergraduate texts on solid mechanics / elasticity. But, none does. Without straining your curiosity any further, let me tell you what that (minor) problem is:

In the past few days at iMechanica, there have been quite a few messages dealing with different aspects of programming, libraries and so on...

It would perhaps be timely, therefore, to ask:

Do you have any opinion about using Java in numerical analysis (NA) / FEM / CFD etc.---i.e., in computational engineering and sciences (CES)?

Do you have any experience or hard data concerning performance of Java vis-a-vis C++ or FORTRAN, esp. for large systems, or for high-performance applications? Any pointers?

Please leave a note... Thanks in advance...

-----

A few clarifications:

In the literature, FEM has sometimes been characterized as a local approach, but IMO this needs to be corrected.

The piecewise continuous trial-functions of FEM can be looked at from two different viewpoints:

(i) If FEM is seen as an expansion method making use of basis functions, then naturally the comparison is with the Fourier-theoretic approaches (and all the derived, consequent or similar ones). The basis functions for the latter are global in the sense they have supports all over the domain. This, indeed, is unlike the limited (piecewise) support of the FEM trial-functions.

It has been quite some time (more than 1.5 years) that I had touched upon the topic of the physical bases of FEM in general, and of the general weighted residual (WR) approach in particular, at iMechanica (see here).

The position I then took was that there is no known physical basis at all for the WR approach---despite its loving portrayals in mathematical terms, or its popularity.

Further, I had also expressed (here and elsewhere) that a basis in physical principles existed for FEM only in a rather limited sense: wherever the energy interpretation was available for the model. (Note, this too is already at variance with what some of the authors have written in books.)