Can I publish an article or thesis about my research without supervisor? I am a bachelor student majoring on computer engineering and working on robotics. Last year as a part of my research, I worked together with a student and one teacher as a supervisor, so we published our article for conference together. But later we finished our research and all of us left the team. Now I am working on other research problem by myself and got some results and want to publish it. But this time I am alone, I have no supervisor on that research problem or any student partner. So I'd like to ask can I submit a paper for conference/journal by myself?
P.S. My current research project has no relationship with old one.
You definitely submit a paper by yourself and if you write a high quality submission, it will be accepted.

When I was early in my research career I found it very helpful to have a collaborator such as a teacher/professor or a postdoc student with publishing experience to collaborate on papers. This often helps catching points or issues that you may overlook within your research as well as providing advice and guidance.