Abstract: In a logging identification method for a small fault based on stress anisotropy and crustal stress types, a magnitude and direction of a current crustal stress are determined by means of logging calculation of the crustal stress, and a transformation location of a crustal stress type is determined; a development location of the small fault is determined according to the transformation location of the crustal stress type; and an included angle between the current crustal stress and the fault is determined according to an amplitude of variation of stress anisotropy. The present disclosure provides the logging identification method for a small fault based on stress anisotropy and crustal stress types. According to the method, prediction cost is low, operability is high, and a prediction result has a reference value for guiding exploration and development of a complex oil and gas reservoir and construction of a gas storage.

Abstract: A Battery Management System (BMS) inspects a battery pack using AC impedance. A controller on the BMS drives a Pulse-Width Modulation (PWM) output signal to an on-board excitation regulator such as a synchronous buck converter that modulates a limited energy unit such as a capacitor with a swept frequency of a PWM input signal. The capacitor modulations are applied to a terminal of the battery pack as an AC excitation signal. Synchronous sampling of the battery pack provides responses to the AC excitation signal. An AC excitation signal current and a battery response voltage are processed and Fourier-transformed to generate a Nyquist plot of the excitation-response data. Curve shifts can indicate worn battery cells. The capacitor generating the AC excitation signal draws little energy from the battery pack so AC impedance inspection can occur during all modes: charging, discharging, and idle modes without an external power supply.