From what I know about reapplying to the same program, it can be an uphill battle but not impossible. I don't think any committee will dismiss an application simply because the applicant had previously applied to the program (although check if there is actually a policy against reapplications). They will, however, probably pay attention to what has changed since you last applied.
You say that you have 2 new pieces of research, but have these resulted in publications (or at least submissions for publication)? If not, they may not carry much weight. If there is anything else about your application that could be considered weak, be sure to address those as much as you can. If your undergraduate GPA was low(er), there isn't much you can do to raise it after the fact. You could, however, demonstrate that you have taken the initiative to take supplemental coursework in the areas in which you are weak, particularly if those areas are applicable to your graduate program. Perhaps ask your research supervisors for letters of recommendation, if they did give those the first time around.
I would also consider applying to more than just your top choice school, just in case (unless you only want to attend this top choice school and nowhere else).
Of course, there is no magic formula for graduate admissions. I think the best you can do is make sure you have addressed any deficiencies in your application from last time and make sure your application in general fits the profile of the schools to which you're applying.