Abstract: Methods for preparation of surfactant-free ultra-small spinel ternary metal oxide nanoparticles are provided. A method comprises dissolving first and second metal salts in deionized water in a specific mole ratio to form a solution comprising two different metal ions, applying a coprecipitation method and adding an alkaline solution to the solution to form a colloidal suspension, wherein a colloid of the colloidal suspension is a metal hydroxide, adjusting the amount and the addition rate of the alkaline solution to form a specific structure of metal hydroxide precipitate; washing and drying the metal hydroxide to form a structured metal hydroxide powder, and applying a calcination method to the structured metal hydroxide powder to form a surfactant-free spinel-type (AB2O4) ternary metal oxide, wherein A and B each respectively comprise a metal element.

Abstract: Methods for preparation of surfactant-free ultra-small spinel ternary metal oxide nanoparticles are provided. A method comprises dissolving first and second metal salts in deionized water in a specific mole ratio to form a solution comprising two different metal ions, applying a coprecipitation method and adding an alkaline solution to the solution to form a colloidal suspension, wherein a colloid of the colloidal suspension is a metal hydroxide, adjusting the amount and the addition rate of the alkaline solution to form a specific structure of metal hydroxide precipitate; washing and drying the metal hydroxide to form a structured metal hydroxide powder, and applying a calcination method to the structured metal hydroxide powder to form a surfactant-free spinel-type (AB2O4) ternary metal oxide, wherein A and B each respectively comprise a metal element.

Abstract: A banknote crack detection method and a banknote crack detection apparatus are provided. The banknote crack detection apparatus includes an image collection unit, configured to collect an optical transmission image of an inputted banknote, a pre-processing unit, configured to receive a banknote image signal collected by the image collection unit, and perform foreground region positioning and cutting on the banknote image signal; a crack detection unit, configured to detect whether a crack exists; and a determining unit, configured to determine whether the banknote is qualified according to a detection result of the crack detection unit; and a control unit, configured to control operation of each of the above units.

Abstract: A banknote crack detection method and a banknote crack detection apparatus are provided. The banknote crack detection apparatus includes an image collection unit, configured to collect an optical transmission image of an inputted banknote, a pre-processing unit, configured to receive a banknote image signal collected by the image collection unit, and perform foreground region positioning and cutting on the banknote image signal; a crack detection unit, configured to detect whether a crack exists; and a determining unit, configured to determine whether the banknote is qualified according to a detection result of the crack detection unit; and a control unit, configured to control operation of each of the above units.