Unfortunately, there are no specific scholarships or grants available exclusively for publishing research papers in the optional subject of Mechanical Engineering. However, there are various funding opportunities that can support research in this field. Here are some options to consider:

1. Institutional Scholarships:
- Many universities and research institutions offer scholarships for graduate students or researchers in Mechanical Engineering. These scholarships may be based on academic merit, research potential, or financial need. It is advisable to check with the specific institution or department for available funding opportunities.

2. Government Scholarships and Grants:
- Government bodies such as the National Science Foundation (NSF) or the Department of Defense (DoD) offer research grants and fellowships in various fields, including Mechanical Engineering. These grants can support research projects, including the publication of research papers. It is essential to explore the respective government agency's website for available funding programs and eligibility criteria.

3. Professional Organizations:
- Professional organizations related to Mechanical Engineering, such as the American Society of Mechanical Engineers (ASME), may provide scholarships or grants for research and publication. These organizations often aim to support the advancement of knowledge in the field and encourage research activities among their members.

4. Corporate Sponsorship:
- Companies and industries related to Mechanical Engineering may offer sponsorships or grants for research projects. These sponsorships can vary in terms of funding amount and requirements. It is worth exploring opportunities with companies that align with your research interests.

5. International Scholarships:
- Some countries or international organizations provide scholarships for international students or researchers to pursue higher education or conduct research. These scholarships can cover various fields, including Mechanical Engineering. Examples include the Fulbright Scholar Program and the Erasmus Mundus Scholarships.

In conclusion, while there are no specific scholarships or grants exclusively for publishing research papers in Mechanical Engineering optional subject, there are various funding opportunities available. It is crucial to explore institutional scholarships, government grants, professional organizations, corporate sponsorships, and international scholarships to support your research and publication endeavors in Mechanical Engineering.