Research on the Comprehensive Evaluation Method for the Automatic Recognition of Raman Spectrum under Multidimensional Constraint.

Raman spectrum contains abundant substance information with fingerprint characteristics. However, due to the huge variety of substances and their complex characteristic information, it is difficult to recognize the Raman spectrum accurately. Starting from dimensions like the Raman shift, the relative peak intensity, and the overall hit ratio of characteristic peaks, we extracted and recognized the characteristics in the Raman spectrum and analyzed these characteristics from local and global perspectives and then proposed a comprehensive evaluation method for the recognition of Raman spectrum on the basis of the data fusion of the recognition results under multidimensional constraint. Based on the common spectrum database of the normal Raman and surface-enhanced Raman of thousands of substances, we analyzed the performance of the evaluation method. It shows that even for the identification of spectra from instruments of low technical specifications, the automatic recognition rate of the sample can reach 98% and above, a great improvement compared with that of the common identification algorithms, which proves the effectiveness of the comprehensive evaluation method under multidimensional constraint.

The Design and Verification of an Active SAMSR Ultrasonic Guided Wave Monitoring System with Ultra-Low Crosstalk.

Due to long propagation distance and high sensitivity to a variety of damages, ultrasonic guided wave technologies have been widely applied in the damage detection or health monitoring of pipe networks and large plate-like structures. However, there are two important problems to be solved when applying this technology; namely, the large scanning time required for monitoring large-scaled structures and the serious crosstalk between the actuation and receiving signals, especially when monitoring hot-spot regions. Therefore, this study mainly designed key parts, such as the matrix switcher and attenuation circuit. The single-actuation and multiple-simultaneous-reception (SAMSR) mechanism based on an analog switching matrix and a low noise charge amplifier circuit was designed and integrated with the SPI control bus to shorten the scanning time. Moreover, a two-stage attenuation circuit with an interlocking isolation structure is presented to effectively isolate the receiving signals from the actuation signals to obtain ultra-low crosstalk even under a high voltage actuation source. In this study, the designed matrix switcher and other components were integrated into the developed ultrasonic guided wave monitoring system. Several experiments were conducted on a stiffened composite structure to illustrate the effectivity of the developed SAMSR ultrasonic guided wave system by comparing the signals collected with those from a commercial ultrasonic guided wave system.

Spontaneous Formation of Random Wrinkles by Atomic Layer Infiltration for Anticounterfeiting.

Continuous developments of innovative anticounterfeiting strategies are vital to restrain the fast-growing counterfeit markets. Physical unclonable function (PUF)-based taggants allow for a practical solution to provide irreproducible codes for strong authentication. Herein, an advanced anticounterfeiting strategy with multiple security levels was successfully developed using screen printing and atomic layer infiltration (ALI) techniques. Macroscale poly(dimethylsiloxane) (PDMS) patterns were fabricated for primary verification. Spontaneous formation of random wrinkles with size in the micrometer scale was achieved on the top surface of screen-printed PDMS patterns due to the anisotropic relief and redistribution of extra compressive stress after Al2O3 infiltration, which can be used for senior authentication by image identification using the artificial intelligence (AI) technique. Furthermore, the complexity and security level of a code, which are proportional to the minutia density, can be adjusted by the morphology of the wrinkles in terms of amplitude and wavelength via the degree of Al2O3 permeation depending on ALI conditions. These spontaneously formed random wrinkles were demonstrated for validation and decoding with AI, exhibiting the merits of being unclonable, nondestructive, universally adaptable, environmentally stable, and mass-producible, and sufficiently adaptable for an industry-suitable authentication strategy.