Q: Is my action regarded as duplicate submission or self-plagiarism?

From your query, here is what we understand of the scenario:

• You have planned to publish two manuscripts in the same research area (ultrasonic data) and perhaps around the same research question. The first research, which is already published, was done individually; the second is a collaborative effort.
• In the first research, you used a new measuring method. We are not sure if you have used this new method in the second research as well, but you are planning to use the data from the first research (obtained using the new method) in the second research. Perhaps you plan to use the data in your background and/or discussion in the second research.
• Apart the data of the new research method (used from the first research), the second research, apart from being a collaborative effort, seems to differ from the first mainly in terms of quantum of data: it will have data “from many more cases with a lot of subjects,” as you have written.

If this is indeed the case, there may indeed be a case of duplicate submission and self-plagiarism; actually, it may more specifically be a case of salami slicing, where a bigger study is presented as smaller studies in multiple publications merely to increase the number of publications. Whatever the case, it seems that the research may not warrant two separate publications. The only consideration here for having two separate papers would be the new research method and to what extent you are using it in both papers.

From what we understand, we suggest that the second research go as an addendum to the first research paper. In this case, you will need to inform the journal editor about it, who could also guide you on how to go about this. Additionally, as the second research has multiple collaborators, you will need to acknowledge their contributions.

Here are some resources to help you in this matter.

• Duplicate publications and simultaneous submissions
• Will my paper be considered a case of self-plagiarism or salami slicing?
• Is it salami slicing if I publish a new study based on my previous published work?
• Tips on writing the Acknowledgments section
• Basics of authorship in academic publishing

As you have correctly mentioned, in the MLA style, the source information is mentioned underneath the tables, irrespective of the number of sources you have used. Often, papers cite three or four different sources below the table. The rule remains the same for a single source and for multiple sources.

Related reading:

• Cite Right: handy advice on citations and references
• Referring to tables and figures in text
• 9 Tips on presenting your tables effectively