I have not submitted material to trade journals, but from what I have picked up...
* They will want to verify that your claims of originality have not already been made by someone else. If someone has prior claim of invention, then your contribution might be an improvement at best.
* They will want submissions to be in a particular format. Find out ahead of time what is their preference. Schematics and illustrations are helpful and welcome (as they are in most presentations).
* They will test your concepts, or, they will consult engineers who can critique your concepts. It is wise to provide references for any unusual statements that are not common knowledge to the readership.
* For financial compensation, they may offer you a standard rate, or they may negotiate an amount.
* By publishing your concepts, you provide readers with your knowledge, making it possible for them to profit. Do you expect an opportunity for yourself to profit as well? Or do you give up that expectation? This is all speculation, of course.
* Have you considered whether you should get your idea patented? Of course that only gives you the right to sue. It does not automatically protect your rights, nor does it guarantee you'll win in court, nor does it guarantee that you'll receive royalties. Getting a patent costs you money. It may cost you thousands of dollars, and there are people who say it may not be worth the expense.