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Junseong Park

Publications and source records attributed to Junseong Park.

2 recordsLinked to original sources

DEPLOY-RL: Active Boundary Discovery and Conservative Certification for Deployable Reinforcement Learning in Safety-Critical Continuous Processes

Reinforcement learning (RL) policies often outperform classical controllers in simulation, yet rarely reach production in safety-critical processes. The barrier is that there is no principled way to answer "Is this policy safe to deploy?" with statistical guarantees. We introduce DEPLOY-RL, a post-training certification framework built on one key insight: deployment certification requires discovering where failures occur (boundary discovery), not measuring how much everywhere (uniform reconstruction). Our contributions: (1) a contract-coupled acquisition function that concentrates sampling on certification-critical boundaries, achieving approximately 2x sample efficiency with a semi-empirical ambiguity reduction bound (domain-calibrated convergence guarantee); (2) conformal risk control providing finite-sample false-go guarantees (<= alpha) under explicit deployment contracts; (3) a three-way decision framework (Deploy/No-Deploy/Abstain) with fail-safe PID/MPC fallback. In simulations on papermaking (industrial digital twin) and Tennessee Eastman (public benchmark), DEPLOY-RL achieves 4.4% false-go rate (vs. 8.6% for the best baseline) while retaining 88.6% policy coverage, the only method achieving <5% false-go with >85% coverage among 14 baselines under our evaluation protocol.

cs.LG↗

Shock Waves and Energy Dissipation in Magnetohydrodynamic Turbulence

Shock waves play an important role in turbulent astrophysical media by compressing the gas and dissipating the turbulent energy into the thermal energy. We here study shocks in magnetohydrodynamic turbulence using high-resolution simulations. Turbulent Mach numbers of $\mathcal{M}_\text{turb}=0.5-7$ and initial magnetic fields of plasma beta $β_0=0.1 - 10$ are considered, targeting turbulences in interstellar and intracluster media. Specifically, we present the statistics of fast and slow shocks, such as the distribution of shock Mach numbers ($M_\text{s}$) and the energy dissipation at shocks, based on refined methodologies for their quantifications. While most shocks form with low $M_\text{s}$, strong shocks follow exponentially decreasing distributions of $M_\text{s}$. More shocks appear for larger $\mathcal{M}_\text{turb}$ and larger $β_0$. Fast shock populations dominate over slow shocks if $β_0\gg1$, but substantial populations of slow shocks develop in the cases of $β\lesssim1$, i.e., strong background fields. The shock dissipation of turbulent energy occurs preferentially at fast shocks with $M_\text{s}\lesssim$ a few to several, and the dissipation at strong shocks shows exponentially decreasing functions of $M_\text{s}$. The energy dissipation at shocks, normalized to the energy injection, $ε_\text{shock}/ε_\text{inj}$, is estimated to be in the range of $\sim0.1-0.5$, except for the case of $\mathcal{M}_\text{turb}=0.5$ and $β_0=0.1$ where the shock dissipation is negligible. The fraction decreases with $\mathcal{M}_\text{turb}$; it is close to $\sim0.4-0.6$ for $\mathcal{M}_\text{turb}=0.5$, while it is $\sim0.1-0.25$ for $\mathcal{M}_\text{turb}=7$. The rest of the turbulent energy is expected to dissipate through the turbulent cascade.

astro-ph.HE↗