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Zijun (Brighton) Liu — ML Engineering & ML Research. Download: ML Engineering Resume · ML Research Resume
General Information
| Full Name | Zijun (Brighton) Liu |
| Location | San Diego, CA |
| liuzijun6688@gmail.com | |
| Phone | 530-220-8681 |
Education
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Sep 2025 - Jun 2027 B.S. Astrophysics, Data Science Minor
University of California, San Diego - GPA: 3.92 (Institutional) | 3.87 (Cumulative) · Phi Beta Kappa
- Applying to M.S. programs in CS / ML for Fall 2027; available for a Summer 2027 internship, Jun - Sep 2027.
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Sep 2023 - Jun 2025 Physics (Astrophysics Emphasis), transferred to UCSD
University of California, Davis - GPA: 3.84
Publications
Experience
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Jun 2026 - Sep 2026 Machine Learning Research Intern
Rothenberg Wealth Strategies · San Diego - Deployed a LightGBM model I trained and selected on walk-forward validation as an unattended production service on a cloud VM: scheduled data ingestion, feature-build and inference phases, duplicate-safe external API calls with daily reconciliation, and a FastAPI + DuckDB ops dashboard.
- Made the live system compute features exactly as in training: fixed feature order and automatic rejection of missing or non-finite inputs.
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Apr 2026 - Jun 2026 AI Engineer Intern
XView LLC · Remote - Built a 5-agent CrewAI content pipeline with retrieval over product docs (Chroma), generating 35 platform-tailored drafts per run across 5 social platforms.
- Set up the evaluation loop (prompt A/B tests, chunking-strategy comparison) that cut factual errors by about 60% and brought the human revision rate of generated drafts to about 30%.
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Jan 2026 - Mar 2026 Machine Learning Research Intern
Rothenberg Wealth Strategies · San Diego - Ran controlled LightGBM experiments over ~2.4M rows of time-series data: feature engineering and ablation across 1,000+ features, label and loss-function variants including a custom objective, and hyperparameter sweeps (Latin hypercube and Optuna) evaluated by walk-forward validation.
- Built the experiment tooling in Python: hyperparameter sweeps defined from config files, a multi-worker queue runner (1,000+ runs per sweep), per-run loss-curve diagnostic notebooks, and an HTML report builder.
- Built a self-supervised VAE with a temporal-convolutional encoder and decoder over ~10M rows of time-series windows.
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Sep 2025 - Dec 2025 Data Science Intern
Himiway Intelligent Technology USA - Refactored notebook analyses into a production ETL and forecasting codebase (SQL/Python, argparse, logging, Makefile) for continuous ingestion.
- Trained and deployed an XGBoost model for store-location and inventory decisions, cutting the decision cycle from 4 weeks to 1.
- Designed and evaluated a months-long in-store A/B test (fat-tire vs. thin-tire e-bikes), analyzing conversion rate and revenue per visitor in Tableau.
Projects
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2026 - Now Self-Supervised Learning on Stellar Light Curves
- First author, with Y. Ma and Prof. C. Theissen (UCSD). Paper accepted at ML4PS @ NeurIPS 2026.
- Pre-trained a convolutional encoder with a GRU latent-prediction objective (PyTorch) on unlabelled TESS light curves; froze it and evaluated the embeddings with linear probes on 10 downstream tasks.
- Concatenated the embeddings with 25 engineered features, improving linear-probe results on 7 of 10 tasks and beating a Conv1D and an MLP trained end-to-end; multi-seed experiments with bootstrap confidence intervals, tracked with Weights & Biases.
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2025 - Now KataGo × LLM — LLM Post-Training & Edge Deployment
- Project lead of a volunteer team. Post-trained Qwen3-8B (LoRA, Hugging Face TRL, vLLM rollouts, Dockerized training) to play 9x9 Go and explain its moves by distilling the KataGo engine: GRPO first, then a rules-SFT / play-SFT / GRPO curriculum on 302k engine-verified examples; first wins vs a classical engine, zero illegal moves.
- Built the evaluation (board-perception probe, top-k agreement, refereed engine ladder) and stabilized GRPO; removed reward hacking, countered entropy collapse with DAPO clip-higher + adaptive entropy control.
- Deployed 4-bit GGUF (llama.cpp) on an 8 GB-VRAM GPU behind a C++ GTP proxy for the Lizzie GUI (~42.5 tok/s, 0.52 s TTFT); served base + 2 LoRA adapters from one vLLM instance to run 3 bots live on OGS. Demo
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2026 ASTR199 — Deep-Learning Inference of Stellar Parameters
- With Prof. C. Theissen, UCSD.
- Engineered a DuckDB ETL pipeline cross-matching ~1M rows across 7 photometric catalogs; built a physics-informed feature space of color indices and absolute magnitudes.
- Built a two-stage deep-learning pipeline that resolved multi-task training collapse with a sequential design and physics-informed features (log g R² 0.52 → 0.83).
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2025 Breaking Barriers Hackathon (AWS × Deloitte × AT&T) — Finalist, Top 8 of 32
- Built a real-time anomaly-detection pipeline: sliding-window spatio-temporal features and an XGBoost classifier with thresholds tuned on PR-AUC for imbalanced data.
- Served inference on AWS Lambda (under 400 ms), streaming alerts to an S3-hosted map dashboard.
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2025 PHY199 — Galaxy Spectra PCA Pipeline
- With Prof. Wittman, UC Davis.
- Automated Python/R preprocessing pipeline for 2,300+ high-dimensional spectra; PCA-based outlier filtering with scikit-learn, interpreting PC1–PC3.
Honors and Awards
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2026 - Phi Beta Kappa, UC San Diego chapter
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2025 - Breaking Barriers Hackathon Finalist — Top 8 of 32 Teams (AWS × Deloitte × AT&T)
Skills
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Languages
- Python, C++, SQL, Bash
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Machine Learning
- PyTorch, self-supervised learning, sequence models (Conv1D-VAE, GRU, TCN), time-series analysis
- LLM post-training (SFT, GRPO, DAPO, LoRA; Hugging Face TRL), RAG, multi-agent pipelines (CrewAI)
- LightGBM, XGBoost, scikit-learn, hyperparameter search (Optuna, Latin hypercube sampling)
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Serving & Infrastructure
- vLLM (multi-LoRA serving), llama.cpp / 4-bit GGUF quantization, C++ REST proxy (cpp-httplib)
- FastAPI, Docker, Linux / systemd, Git, AWS (Lambda, S3)
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Data & Tracking
- DuckDB, Polars, pandas, PostgreSQL, Parquet, Weights & Biases, Tableau
Leadership
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2025 - Now Project Lead
KataGo × LLM volunteer team -
Sep 2024 - Jun 2025 President & Co-Founder
Go Club at UC Davis - Grew membership to 30+ members; coordinated with ACGA and universities to run inter-school competitions and community events.
- Led cross-cultural, mixed-skill communications; organized weekly programs and external collaborations.