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Endogenous vs.Exogenous Disturbances in Closed Granular Systems: Empirical Evidence for Objective Systemic Deviation
Summary
This study is basic physics research about how beans, beads, and plastic particles behave when scooped or measured in containers—it's not a health study. Researchers found that random variation in these systems comes from two separate sources: natural randomness in how particles settle (even with no outside interference) and mechanical disturbance from the act of scooping or handling. While this doesn't directly relate to human health or microplastics exposure, the measurement techniques developed here could eventually help scientists more accurately measure small particles (including microplastics) in food, water, or environmental samples.
Probabilistic distribution deviations in closed granular sampling systems are a fundamental phenomenon widely observed in statistical physics and powder engineering. Existing studies tend to attribute such distribution shifts collectively to environmental noise, microscopic thermal motion, or external mechanical interference, yet lack controlled comparative experiments to isolate the sources of systematic disturbance, nor have they established a standardized quantitative observational framework. In this paper, using black-yellow beans, stainless steel beads, and plastic particles as experimental carriers, we constructed three controlled systems—a no-external-force dynamic recirculation pool as a simulation baseline, quantitative scooping with force measurement, and manual grasping as auxiliary validation—to achieve separate observation and quantitative characterization of two sources of fluctuation. The dynamic simulation results demonstrate that, in the absence of external input, the granular system inherently exhibits stable endogenous probabilistic deviations. The instantaneous peak force measured by an electronic balance can quantitatively characterize the exogenous mechanical disturbance introduced by scooping and dispensing, while manual operations exhibit stable differences in external force amplitude between hands. The total probabilistic deviation observed in the physical system is the linear superposition of endogenous disturbance and exogenous disturbance. To provide a unified description of the two types of fluctuations and their superposition effects across this series of studies, this paper simplifies and defines endogenous disturbance, exogenous disturbance, and generalized disturbance based on existing fluctuation theory, with the nomenclature serving solely as a subdivision tool for analytical clarity rather than introducing new physical quantities. This study establishes a low-cost, reproducible observational and quantitative analysis paradigm for binary fluctuations, accomplishes conceptual accreditation of the sources of disturbance in granular systems, and provides a unified empirical baseline for subsequent series studies on multi-physics-field disturbances and cross-scale evolutionary mechanisms.