If somebody copies a huge part from your own article or thesis, and publish it on a journal as if it is his own work, what should you do? Does anybody experience this?
A stolen part from your thesis then published means that the published work is done without peer reviewers or plagiarism check that never happen in a respected journal! Predatory journals are big problem for good science, if something stolen from your work then published in a predatory journal so forget to claim nothing work with them. Scientific stealing is becoming a phenomena that supported by predatory journal. I see no powerful law to stop these journals! I suffered a lot and have a phobia from them, these journals send me something to review, my response is always to block them.
I'd contact first the magazine that published, describing the case, without supplying evidence in the first contacts, to know about their policies.
If plagiarism took place in your same country, you can contact the university or courts to have a case, if outside, the consular section of your country's diplomat services could provide you with a list of 'trustable' attorneys there to fill a demand, but litigation is expensive and long to solve.
Don't expect too much, Ludwig van Beethoven transcribed to one of the movements in a Symphony a composition by Johann Sebastian Bach, who in turn was 'inspired in peasant's music'. 'Copy and paste', we would say today.
The concept by Saskia Sassen, who received a 'principality of Asturias' price, of: 'Global City', sound same as Marshall McLuhan's: 'Global Village'; the pieces by Joaquin Rodrigo: 'Concierto de Aranjuez', 'Fantasy for a Gentleman', remind works of Spanish renaissance guitar composers: L de Milan, Valderrabano, Gaspar Sanz,...
I attach an image of a 1967 high school publication, showing what for me is almost same as 'Bob Sponge'. The author of drawing, José María Gaytán de Ayala, died recently of a Prostate cancer.
The 1988 movie: D.O.A., Annabel Jankel and Rocky Morton, shows an extreme case of plagiarism.
When attending Sunday mass in Trier, Germany, I heard in the Liebfrauenkirche (German for 'Church of Our Beloved Lady'), a music entry for a Gregorian singing that for me was very similar to Cesar Frank's: 'Prelude, fugue and variation'.
Ohio Express': 'Mercy', contains a phrase heard in the Middle Age music: 'La Suite Meurtrière'.
PMID 27871718 is about Lathyrism, an alimentary disease from a toxic in vetch flour, that had an outbreak in the hunger times that followed Spanish civil war. In the Madrid Jiménez Díaz Foundation, a teaching and research hospital, when an USA visitor came, they talk him about the research regarding this, including studies in pregnant rodents, and many more. When he came back to the States, he reproduced in his lab all the Spanish research in just one month. and published it in advance of the Spanish group.