Update Roman Petrov fellow profile (#2854)

* updated page

* add photo

Author: pingmar

_fellows/2026/pingmar.md

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+---
+layout: fellow
+pagetype: fellow
+shortname: roman-petrov
+permalink: /fellows/roman-petrov.html
+fellow-name: Roman Petrov
+title: Roman Petrov - IRIS-HEP Fellow
+active: True
+dates:
+  - start: 2025-06-23
+    end: 2025-09-15
+  - start: 2026-06-08
+    end: 2026-08-31
+photo: /assets/images/team/fellows-2026/Roman-Petrov.jpg
+institution: National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute"
+e-mail: petrov.romash@gmail.com
+focus-area: Analysis Systems (AS)
+challenge-area:
+projects:
+- project_title: Developing a Pythonic tool for smoothing histograms
+  project_goal: >
+    Develop a user-friendly Python package that implements multiple histogram smoothing algorithms specifically designed for high-energy physics analyses, with integration into the Scikit-HEP ecosystem and comprehensive validation frameworks to help physicists reduce statistical noise in histograms while preserving underlying signal characteristics.
+  mentors:
+  - Mohamed Aly (Princeton University)
+  - Alexander Held (University of Wisconsin–Madison)
+  - Matthew Feickert (University of Wisconsin–Madison)
+  proposal: /assets/pdf/fellows-2025/UKR004-proposal-Roman-Petrov.pdf
+- project_title: Overcoming Vertex Reconstruction Limitations under the High-Density HL-LHC Pileup Environment
+  project_goal: >
+    Investigate and resolve vertex reconstruction inefficiencies under HL-LHC pileup conditions by characterizing algorithmic failure modes and developing targeted improvements to seeding, clustering, and fitting stages, validated against baseline methods on simulated HL-LHC datasets.
+  mentors:
+  - Ariel Schwartzman
+  proposal: /assets/pdf/fellows-2026/UKR006-proposal-Roman-Petrov.pdf
+presentations:
+current_status:
+github-username: pingmar
+linkedin-profile: https://www.linkedin.com/in/petrov-roman/
+funding-source: other
+ukraine: true
+---