arXiv subjects

Baiqing Li

Publications and source records attributed to Baiqing Li.

4 recordsLinked to original sources

arXiv2026

Induced electromotive force of a thin metal rod in the alternating electromagnetic field of Helmholtz coil: experimental results and theoretical analysis

We apply a thin metal rod (copper rod) as a probe in the alternating magnetic field generated by a Helmholtz coil, and measure the variation of the induced electromotive force (EMF) on the metal rod at different radial positions of Helmholtz coil. Experimental results show that the induced EMF is zero when the center of the metal rod passes through the center of the cylindrical magnetic field inside the Helmholtz coil. When the metal rod is displaced from the center of field to different radial positions, the induced EMF gradually increases from zero, reaches a maximum at a certain position, and then decreases monotonically as the radial distance continues to increase. At the position where the induced EMF reaches its maximum, the metal rod intersects the radial cross-section of the internal magnetic field of the Helmholtz coil at two points, with a small central portion of the rod located inside the Helmholtz coil and the two end portions outside the coil. To explain the experimental phenomena, we construct four simplified models of the magnetic field distribution based on the actual field distribution of the Helmholtz coil to quantitatively investigate the radial variation of the induced EMF along the metal rod. Our theoretical results show that the four models yield similar results and can all qualitatively explain the experimental data curves, particularly reproducing well the variation trend of the induced EMF and the position of the extremum point. The result of piecewise function fitting model is quantitatively in good agreement with the experimental data. This work is also very much helpful and instructive for undergraduate-level students.

physics.class-ph↗

arXiv2026

CARE: Context-Aware Ranking Evolution with Executable Scoring Programs for Budgeted Reaction Optimization

High-throughput experimentation can evaluate many reaction conditions, yet combinatorial condition spaces still exceed the available experiment budget. This makes experiment selection a sequential decision problem: each new condition must be chosen from limited observations before its outcome is known. LLMs can express task-specific selection logic. A direct recommendation, however, is neither a persistent executable object that can be validated and revised nor an independently auditable decision rule. We introduce CARE, a reference-conditioned controller that separates program synthesis from experiment selection. An LLM writes an executable scoring program that ranks the remaining conditions, while a non-LLM reference policy supplies a numerical candidate and support summary. CARE forms an optional alternative from the program, applies a reference-conditioned intervention gate to compare it with the reference, and records the decision before the selected outcome is revealed. Each new outcome updates controller state and can trigger retention, revision, or regeneration of the active program. This outcome-guided program evolution changes the scoring logic without updating the LLM parameters. In matched offline replay with 30 seeds on eight reaction-optimization tasks, CARE attains the lowest normalized regret, the highest normalized best-so-far AUC, and the highest Top-1% Success@15 among the evaluated methods. These results support using a scoring program written by an LLM as one component of a reference-conditioned optimizer rather than as a standalone experiment selector.

cs.LG↗

arXiv2009

Efficient evaluation of accuracy of molecular quantum dynamics using dephasing representation

Ab initio methods for electronic structure of molecules have reached a satisfactory accuracy for calculation of static properties, but remain too expensive for quantum dynamical calculations. We propose an efficient semiclassical method for evaluating the accuracy of a lower level quantum dynamics, as compared to a higher level quantum dynamics, without having to perform any quantum dynamics. The method is based on dephasing representation of quantum fidelity and its feasibility is demonstrated on the photodissociation dynamics of CO2. We suggest how to implement the method in existing molecular dynamics codes and describe a simple test of its applicability.

physics.chem-ph↗

arXiv2006

Kinetics and thermodynamics of electron transfer in Debye solvents: An analytical and nonperturbative reduced density matrix theory

A nonperturbative electron transfer rate theory is developed based on the reduced density matrix dynamics, which can be evaluated readily for the Debye solvent model without further approximation. Not only does it recover for reaction rates the celebrated Marcus' inversion and Kramers' turnover behaviors, the present theory also predicts for reaction thermodynamics, such as equilibrium Gibbs free-energy and entropy, some interesting solvent-dependent features that are calling for experimental verification. Moreover, a continued fraction Green's function formalism is also constructed, which can be used together with Dyson equation technique, for efficient evaluation of nonperturbative reduced density matrix dynamics.

quant-ph↗