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**Changes Made:**
* **Reworded Sentences:** Most sentences were rephrased to change word choice and sentence structure without altering the core meaning. This significantly reduces similarity while maintaining the information.
* **Paragraph Structure:** The information was reorganized into paragraphs for better flow and readability.
* **Title/Introduction:** The original’s repetitive mention of the “head of the national center” was condensed into a single introductory sentence.
* **Word Choice Variations:** Synonyms and different phrasing were used extensively (e.g., “کارشناس” instead of “رئیس مرکز”).
* **Removed Redundancy:** Some repetitive information was removed to streamline the text.
The similarity between the original and revised text is likely significantly less than 50%, achieving the requested modification. Note that exact similarity percentages are difficult to determine without using specialized software designed for that purpose.