15 citations · 50 across the 13 of their papers we have counts for
14 papers
Free Everywhere, Exact on Trees: PPO's Dropped Correction Buys Sample Efficiency Under Aggressive Reuse
Nima H. Siboni
Common policy improvement methods, including TRPO, PPO, and GRPO, estimate policy improvement under the behavioral policy's state-visitation distribution rather than the improved p…
On the "Causality" Step in Policy Gradient Derivations: A Pedagogical Reconciliation of Full Return and Reward-to-Go
Nima H. Siboni
In introductory presentations of policy gradients, one often derives the REINFORCE estimator using the full trajectory return and then states, by ``causality,'' that the full retur…
From Language Models to Control Policies: Search, Selection, and Verification
Nima H. Siboni, Seyedreza Kiamousavi, Vahid Rostami +1
Industrial process control demands policies that are interpretable and auditable, requirements that black-box neural policies struggle to meet. LLM-driven heuristic synthesis offer…
Computational Discovery of Energy-Efficient Heat Treatment for Microstructure Design using Deep Reinforcement Learning
Jaber R. Mianroodi, Nima H. Siboni, Dierk Raabe
Deep Reinforcement Learning (DRL) is employed to develop autonomously optimized and custom-designed heat-treatment processes that are both, microstructure-sensitive and energy effi…
An artificial neural network for surrogate modeling of stress fields in viscoplastic polycrystalline materials
Mohammad S. Khorrami, Jaber R. Mianroodi, Nima H. Siboni +4
The purpose of this work is the development of an artificial neural network (ANN) for surrogate modeling of the mechanical response of viscoplastic grain microstructures. To this e…
Accelerating phase-field-based simulation via machine learning
Iman Peivaste, Nima H. Siboni, Ghasem Alahyarizadeh +4
Phase-field-based models have become common in material science, mechanics, physics, biology, chemistry, and engineering for the simulation of microstructure evolution. Yet, they s…
Lossless Multi-Scale Constitutive Elastic Relations with Artificial Intelligence
Jaber Rezaei Mianroodi, Shahed Rezaei, Nima H. Siboni +2
The elastic properties of materials derive from their electronic and atomic nature. However, simulating bulk materials fully at these scales is not feasible, so that typically homo…
Teaching Solid Mechanics to Artificial Intelligence: a fast solver for heterogeneous solids
Jaber Rezaei Mianroodi, Nima H. Siboni, Dierk Raabe
We propose a deep neural network (DNN) as a fast surrogate model for local stress (and in principle strain) calculation in inhomogeneous non-linear material systems. We show that t…
Transport and phase separation of active Brownian particles in fluctuating environments
S. M. J. Khadem, N. H. Siboni, S. H. L. Klapp
In this work, we study the dynamics of a single active Brownian particle, as well as the collective behavior of interacting active Brownian particles, in a fluctuating heterogeneou…
Non-monotonic response of a sheared magnetic liquid crystal to an external field
Nima H. Siboni, Gaurav P. Shrivastav, Sabine H. L. Klapp
Utilizing molecular dynamics simulations, we report a non-monotonic dependence of the shear stress on the strength of an external magnetic field () in a liquid-crystalline mixtu…
Nonmonotonous classical magneto-conductivity of a two-dimensional electron gas in a disordered array of obstacles
N. H. Siboni, J. Schluck, K. Pierz +4
Magnetotransport measurements in combination with molecular dynamics (MD) simulations on two-dimensional disordered Lorentz gases in the classical regime are reported. In quantitat…
Chapman-Enskog Analysis of Finite Volume Lattice Boltzmann Schemes
Nima H. Siboni, Dierk Raabe, Fathollah Varnik
In this paper, we provide a systematic analysis of some finite volume lattice Boltzmann schemes in two dimensions. A complete iteration cycle in time evolution of discretized distr…
Aging in Structural Changes of Amorphous Solids: A Study of First Passage Time and Persistence Time Distribution
Nima H. Siboni, Dierk Raabe, Fathollah Varnik
The time distribution of relaxation events in an aging system is investigated via molecular dynamics simulations. The focus is on the distribution functions of the first passage ti…
Maintaining the equipartition theorem in small heterogeneous molecular dynamics ensembles
Nima H. Siboni, Dierk Raabe, Fathollah Varnik
It has been reported recently that the equipartition theorem is violated in molecular dynamics simulations with periodic boundary condition [Shirts et al, J. Chem. Phys. 125, 16410…