A nondestructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity

Abstract

The present application discloses a method for nondestructive evaluation of mother-of-pearl quality based on three-dimensional structural porosity, relating to the technical field of nondestructive microscopic identification of mother-of-pearl in traditional Chinese medicine. The method comprises calcining raw mother-of-pearl at various calcination temperatures using a bright calcination method to obtain multiple processed products with different degrees of processing; performing micro-CT scanning on the raw mother-of-pearl and each processed product to obtain a plurality of projection images; reconstructing three-dimensional images based on the projection images using a phase recovery algorithm and an iterative reconstruction algorithm to generate three-dimensional data; performing pore segmentation using an image segmentation algorithm based on the three-dimensional data to calculate the porosity of the raw mother-of-pearl and each processed product; and determining the quality grade of the raw mother-of-pearl and each processed product based on the porosity of the raw mother-of-pearl and each processed product and the relationship between porosity, calcination temperature, and sample quality. The present application can achieve nondestructive evaluation of mother-of-pearl quality and improve the accuracy of mother-of-pearl quality evaluation.

Description

Technical Field

[0001] The present application relates to the technical field of non-destructive microscopic identification of traditional Chinese medicine mother-of-pearl, and in particular to a non-destructive evaluation method for the quality of mother-of-pearl based on the porosity of the three-dimensional structure. Background Art

[0002] Pearl mother-of-pearl is a major representative of marine traditional Chinese medicines, and is often processed through the calcination method. Traditional methods for identifying the quality of pearl mother-of-pearl include physical identification, microscopic identification, and physical and chemical identification. Physical identification relies on observing its round or irregular flaky morphology and pearl-like luster. Although simple and intuitive, it is easily affected by sample integrity, resulting in inaccurate identification results. Microscopic identification uses a polarizing microscope to observe the layered structure and overlapping prismatic layers. Although it can distinguish counterfeits, it requires specialized equipment and technical support, otherwise the accuracy of the identification results cannot be guaranteed. Physical and chemical identification uses methods such as dilute hydrochloric acid reaction (bubble generation), burning test (calcium carbonate decomposition), and ultraviolet fluorescence (light blue-white). Although these methods are highly specific and rapid, some methods are destructive and rely on precision instruments, making it difficult to guarantee the accuracy of the identification results.

[0003] In summary, how to provide a more accurate non-destructive evaluation method for mother-of-pearl quality and improve the accuracy of mother-of-pearl quality evaluation has become a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0004] The purpose of this application is to provide a non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity, which can realize non-destructive evaluation of mother-of-pearl quality and improve the accuracy of mother-of-pearl quality evaluation.

[0005] To achieve the above objectives, this application provides the following solutions.

[0006] A non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity specifically comprises the following steps.

[0007] The raw mother-of-pearl was calcined at various calcination temperatures using the open calcination method to obtain multiple processed products with different degrees of processing.

[0008] Micro-CT scanning was performed on the raw mother-of-pearl product and each of the processed products to obtain several projection images.

[0009] According to the projection images, a phase recovery algorithm and an iterative reconstruction algorithm are used to perform three-dimensional image reconstruction to generate three-dimensional data; the three-dimensional data includes a phase contrast micro-CT three-dimensional reconstructed image and a corresponding three-dimensional voxel matrix.

[0010] Based on the three-dimensional data, an image segmentation algorithm is used to perform pore segmentation, and the porosity of the raw mother-of-pearl product and each of the processed products is calculated.

[0011] The quality grade of the raw mother-of-pearl product and each of the processed products is determined based on the porosity of the raw mother-of-pearl product and each of the processed products, combined with the relationship between porosity, calcination temperature and sample quality.

[0012] Optionally, micro-CT scanning is performed on the raw mother-of-pearl product and each of the processed products to obtain a plurality of projection images, which specifically includes the following steps.

[0013] The micro CT scanning parameters of the micro CT system are determined according to the changes in the brightness of the X-rays when the X-rays penetrate the raw mother-of-pearl product and each of the processed products.

[0014] Based on the micro-CT scanning parameters, the micro-CT system is used to perform micro-CT scanning on the raw mother-of-pearl product and each of the processed products to obtain projection images of the raw mother-of-pearl product and each of the processed products.

[0015] Optionally, the micro-CT system includes an X-ray source for emitting X-rays, and a filter, a monochromator, a sample stage and an X-ray detector arranged in sequence along the direction of the X-rays.

[0016] The filter is used to filter the X-rays and remove the stray scattered rays.

[0017] The monochromator is used to adjust the energy of the X-rays.

[0018] The sample stand is used to fix the raw mother-of-pearl product and each of the processed products.

[0019] The X-ray detector is used to collect projection images of the raw mother-of-pearl product and each of the processed products.

[0020] Optionally, based on the plurality of projection images, a phase recovery algorithm and an iterative reconstruction algorithm are used to perform three-dimensional image reconstruction to generate three-dimensional data, which specifically includes the following steps.

[0021] Based on the several projection images, a phase recovery algorithm is used to reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products.

[0022] According to the refractive index distribution of the raw mother-of-pearl product and each of the processed products, an iterative reconstruction algorithm is used to perform three-dimensional CT reconstruction to generate three-dimensional data of the raw mother-of-pearl product and each of the processed products.

[0023] Optionally, before the step of reconstructing the refractive index distribution of the raw mother-of-pearl product and each of the processed products using a phase recovery algorithm based on several of the projection images, the non-destructive evaluation method of mother-of-pearl quality based on three-dimensional structural porosity also includes the following steps.

[0024] Each of the projection images is subjected to geometric correction and noise filtering to obtain a preprocessed projection image; the preprocessed projection image is used as the projection image to reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products based on a phase recovery algorithm.

[0025] Optionally, the iterative reconstruction algorithm is an FDK algorithm.

[0026] Optionally, based on the three-dimensional data, an image segmentation algorithm is used to perform pore segmentation, and the porosity of the raw mother-of-pearl product and each of the processed products is calculated, which specifically includes the following steps.

[0027] Based on the three-dimensional data, an image segmentation algorithm is used to extract a pore-matrix binary three-dimensional structural model.

[0028] Based on the pore-matrix binary three-dimensional structural model, the pore volume and total sample volume of the raw mother-of-pearl and each of the processed products were determined.

[0029] The porosity of the raw mother-of-pearl product and each of the processed products is calculated based on the pore volume of the raw mother-of-pearl product and each of the processed products and the total volume of the sample.

[0030] Optionally, the image segmentation algorithm is an Otsu algorithm or an image segmentation algorithm based on a U-Net deep learning model.

[0031] Optionally, the porosity of the raw mother-of-pearl product and each of the processed products is calculated using the following formula:

[0032] ε=V1 / V2×100%;

[0033] Where ε is the porosity, V1 is the pore volume, and V2 is the total volume of the sample.

[0034] Optionally, the quality levels include high, medium and low levels.

[0035] The porosity value range corresponding to the high grade is: ε>40%.

[0036] The calcination temperature range corresponding to the high grade is: T>800℃.

[0037] The porosity value range corresponding to the medium grade is: 5%≤ε≤40%.

[0038] The calcination temperature range corresponding to the medium grade is: 400°C≤T≤800°C.

[0039] The porosity value range corresponding to the low grade is: ε<5%.

[0040] The calcination temperature range corresponding to the low grade is: T<400℃.

[0041] Where ε is the porosity and T is the calcination temperature.

[0042] According to the specific embodiments provided in this application, this application has the following technical effects:

[0043] The present application provides a method for non-destructive evaluation of mother-of-pearl quality based on three-dimensional structural porosity. Micro-CT scanning technology is used to obtain projection images by performing micro-CT scanning on raw mother-of-pearl and various processed products. Three-dimensional image reconstruction is then performed by using a phase recovery algorithm and an iterative reconstruction algorithm to non-destructively obtain three-dimensional data of the raw mother-of-pearl and different processed products. Porosity segmentation is then performed using an image segmentation algorithm, and the porosity of the raw mother-of-pearl and various processed products is calculated. Combined with the relationship between porosity, calcination temperature and sample quality, the quality grade of the raw mother-of-pearl and various processed products can be non-destructively determined. The present application combines micro-CT scanning technology, three-dimensional image reconstruction technology, pore segmentation technology and porosity quantitative evaluation technology, and integrates multiple algorithms such as phase recovery algorithm, iterative reconstruction algorithm and image segmentation algorithm to realize the porosity quantitative evaluation of mother-of-pearl quality based on the three-dimensional microstructure of raw mother-of-pearl and processed products, thereby improving the accuracy of mother-of-pearl quality evaluation. There is no need to damage samples such as raw mother-of-pearl and processed products, nor is there any need to use a polarizing microscope to observe the layered arrangement structure and prismatic layer overlapping characteristics, and there is no reliance on precision instruments for physical and chemical identification. This achieves efficient, rapid and non-destructive mother-of-pearl quality evaluation and can ensure the accuracy of mother-of-pearl quality evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 A schematic flow chart of a method for non-destructive evaluation of mother-of-pearl quality based on three-dimensional structural porosity provided in one embodiment of the present application.

[0046] Figure 2Schematic diagram of the structure of the X-ray micro-CT experimental device used in the non-destructive evaluation method of mother-of-pearl quality based on three-dimensional structural porosity provided in one embodiment of the present application.

[0047] Figure 3 This is a schematic diagram of the three-dimensional structure of a raw mother-of-pearl product provided in one embodiment of the present application.

[0048] Figure 4 This is a schematic diagram of the three-dimensional structure of the raw mother-of-pearl provided in one embodiment of the present application after being processed at 400°C for 1 hour.

[0049] Figure 5 This is a schematic diagram of the three-dimensional structure of the raw mother-of-pearl provided in one embodiment of the present application after being processed at 600°C for 1 hour.

[0050] Figure 6 This is a schematic diagram of the three-dimensional structure of the raw mother-of-pearl provided in one embodiment of the present application after being processed at 800°C for 1 hour.

[0051] Reference numerals:

[0052] 1-X-ray source; 2-insert; 3-filter; 4-monochromator; 5-sample stage; 6-X-ray detector. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] In response to the limitations of traditional methods for identifying mother-of-pearl quality, modern analytical technologies have achieved breakthroughs through high-precision, non-destructive, and multi-dimensional testing. For example, scanning electron microscopy (SEM) can magnify the layered structure and overlapping prismatic layers of mother-of-pearl down to the nanometer scale, with a resolution far exceeding that of traditional microscopic identification, and can intuitively distinguish between natural and artificial imitations. X-ray diffraction (XRD) analyzes the ratio of aragonite to calcite to determine the crystal form of calcium carbonate, accurately identifying the mineral composition of mother-of-pearl and avoiding the damage to samples caused by traditional physical and chemical methods. Fourier transform infrared spectroscopy (FTIR) combined with 3440 cm -1 The organic matrix absorption peak at 873 cm -1 CO3 2-Vibrational peaks and other characteristic peaks enable joint detection of organic and inorganic components with high sensitivity and without the need for pretreatment. Inductively coupled plasma mass spectrometry (ICP-MS) can quantify trace elements such as Sr (strontium) and Mg (magnesium), and combined with statistical models, can trace origin, solving traceability issues that traditional methods cannot achieve. Raman spectroscopy uses molecular vibration information to rapidly and non-destructively identify mother-of-pearl authenticity, making it suitable for on-site testing. HPLC (high-performance liquid chromatography) fingerprinting rapidly analyzes the authenticity and quality of medicinal materials through methods such as shared peaks and similarity evaluation, providing a comprehensive overview of the types and contents of chemical components in medicinal materials and has been widely used in the quality control of traditional Chinese medicines. These modern technologies address the shortcomings of traditional methods in resolution, specificity, and non-destructive testing, significantly improving identification efficiency and accuracy. However, the equipment is costly and requires specialized personnel.

[0055] Judging from the existing quality standards for mother-of-pearl and related research reports, most of the current quality control measures are based on the content of calcium carbonate. However, the content of calcium carbonate is difficult to reflect the intrinsic pharmacological activity and lacks specificity. It cannot fully reflect the characteristics of the medicinal material and the impact of the processing technology on the quality. At the same time, it has little reference value for market supervision and it is difficult to fundamentally control the intrinsic quality of the medicinal material. In addition, the mechanism of the calcination method for processing mother-of-pearl is still unclear, the processing methods vary greatly, and the quality standards are not unified. This leads to large differences in the quality of mother-of-pearl medicinal pieces, which seriously affects the safety and effectiveness of clinical medication. Given that the research on the basic substance of the efficacy of mother-of-pearl is weak and its mechanism of action is still unclear, it is crucial to establish a simple and effective new quantitative evaluation method to ensure the quality of marine Chinese medicinal materials such as mother-of-pearl and their rational development and utilization.

[0056] Microscopic computed tomography (Micro-CT) technology is developing rapidly. CT scanners use X-rays to penetrate an object at multiple angles and reconstruct cross-sectional images using a computer, enabling three-dimensional nondestructive testing. Its core principle is to exploit differences in tissue absorption of X-rays to generate high-resolution cross-sectional images. It is now widely used in disease diagnosis, industrial flaw detection, and cultural relic analysis. Micro-CT, a sophisticated extension of CT technology, uses a microfocus X-ray source (focal spot size <5μm) and a high-resolution flat-panel detector (pixel size 10-50μm), increasing spatial resolution to submicron levels (0.5-50μm), a 2-3 orders of magnitude improvement over conventional CT. Its core principle is to obtain thousands of projection images by rotating the sample 360°. Using a filtered back-projection algorithm, the 3D volume data is reconstructed, enabling non-destructive "virtual slice" observation. In recent years, micro-CT has become increasingly popular in fields such as biomedicine and engineering physics.

[0057] Micro-CT demonstrates its advantages in the field of Traditional Chinese Medicine (TCM) quality control. It can non-destructively analyze the fine internal structures of medicinal materials, such as the layered aragonite structure of mother-of-pearl and the body cavity of Cordyceps sinensis larvae, while also accurately identifying insect holes, moldy mycelial networks, and adulterants. Combined with energy spectrum techniques (such as dual-energy CT), it can distinguish differences in chemical composition, such as the calcium-to-phosphorus ratio of cowhide and donkey-hide collagen in donkey-hide gelatin. Furthermore, combined with artificial intelligence algorithms, it can establish a digital evaluation system for key parameters such as porosity and mineralization of medicinal materials. Compared to traditional microscopic identification (destructive sectioning and limited field of view) and HPLC (chemical component analysis only), micro-CT can simultaneously achieve three-dimensional quantitative analysis of morphology, composition, and structure while maintaining the integrity of the medicinal material, providing an intelligent solution for the standardization and authenticity verification of TCM.

[0058] In summary, there is an urgent need for a more accurate non-destructive evaluation method for mother-of-pearl quality, which uses porosity as a quantitative indicator to measure the degree of processing and quality grade of mother-of-pearl, in order to form a model that is different from the previous quality control model based on the content limit of chemical indicators, and provide new ideas and references for the quality control research of marine mineral traditional Chinese medicine.

[0059] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0060] like Figure 1 As shown, this embodiment proposes a non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity, and the non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity specifically includes the following steps.

[0061] Step S1: calcining raw mother-of-pearl at various calcination temperatures using a bright calcination method to obtain a plurality of processed products with different degrees of processing.

[0062] Raw mother-of-pearl refers to the raw material used in the preparation of traditional Chinese medicine (TCM) mother-of-pearl. Its dense structure and high calcium carbonate content provide the foundation for subsequent calcination. Raw mother-of-pearl is uncalcined. By calcining it at high temperatures, it can be calcined into its corresponding processed product.

[0063] The open-calcination method, which involves calcining pearls without air, is suitable for easily calcined minerals, animal shells, and fossilized medicinal materials. This method involves high-temperature oxidation and decomposition of the calcium carbonate (calcium carbonate) in raw mother-of-pearl, creating a porous calcium oxide (CaO) structure. This is a key step in enhancing its efficacy and quality.

[0064] In this embodiment, each raw mother-of-pearl product is calcined at various calcination temperatures (e.g., 400°C, 600°C, 800°C) by the open calcination method to obtain processed products with different degrees of processing. The raw mother-of-pearl product and the processed products with different degrees of processing are simultaneously used as samples to be tested.

[0065] Step S2: Perform micro-CT scanning on the raw mother-of-pearl product and each of the processed products to obtain a plurality of projection images.

[0066] In this embodiment, step S2 performs micro CT scanning on the raw mother-of-pearl product and each of the processed products to obtain a plurality of projection images, which specifically includes the following steps.

[0067] Step S21: determining the micro-CT scanning parameters of the micro-CT system according to the brightness change of the X-rays when the X-rays penetrate the raw mother-of-pearl product and each of the processed products.

[0068] Step S22: Based on the micro-CT scanning parameters, use the micro-CT system to perform micro-CT scanning on the raw mother-of-pearl product and each of the processed products to obtain projection images of the raw mother-of-pearl product and each of the processed products.

[0069] This embodiment uses a micro-CT system to perform micro-CT scanning. The micro-CT system includes an X-ray source 1 for emitting X-rays, and a filter 3, a monochromator 4, a sample table 5, and an X-ray detector 6 arranged in sequence along the direction of the X-rays. Figure 2 As shown, the filter 3 is used to filter the X-rays and remove stray scattered rays. The monochromator 4 is used to adjust the energy of the X-rays. The sample table 5 is used to hold the raw mother-of-pearl product and each processed product. The X-ray detector 6 is used to collect projection images of the raw mother-of-pearl product and each processed product.

[0070] In an exemplary embodiment, an insert 2 may be further provided in the micro-CT system. The insert 2 is located between the X-ray source 1 and the filter 3. Figure 2 As shown, insert 2 is an optional accessory or module used to enhance the micro-CT system's functionality, adapt to specific experimental needs, or optimize imaging results. For example, insert 2 includes various optical devices. This expands the micro-CT system's application range, making it suitable for more complex samples or experimental conditions.

[0071] Step S3: Based on the projection images, a phase recovery algorithm and an iterative reconstruction algorithm are used to perform three-dimensional image reconstruction to generate three-dimensional data; the three-dimensional data includes a phase contrast micro-CT three-dimensional reconstructed image and a corresponding three-dimensional voxel matrix.

[0072] In this embodiment, step S3 performs three-dimensional image reconstruction based on the plurality of projection images using a phase recovery algorithm and an iterative reconstruction algorithm to generate three-dimensional data, which specifically includes the following steps.

[0073] Step S31: Reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products using a phase recovery algorithm based on the plurality of projection images.

[0074] Step S32: Performing three-dimensional CT reconstruction based on the refractive index distributions of the raw mother-of-pearl and each of the processed products using an iterative reconstruction algorithm to generate three-dimensional data of the raw mother-of-pearl and each of the processed products. The iterative reconstruction algorithm uses the Feldkamp Davis Kress (FDK) algorithm.

[0075] In an exemplary embodiment, before reconstructing the refractive index distribution of the raw mother-of-pearl product and each of the processed products using a phase recovery algorithm based on several of the projection images in step S31, the non-destructive evaluation method of mother-of-pearl quality based on three-dimensional structural porosity also includes an image preprocessing process, which specifically includes the following steps.

[0076] Step S30, perform geometric correction and noise filtering on each of the projection images to obtain a preprocessed projection image; the preprocessed projection image is used as the projection image to reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products based on a phase recovery algorithm.

[0077] Step S4: Based on the three-dimensional data, an image segmentation algorithm is used to perform pore segmentation, and the porosity of the raw mother-of-pearl product and each of the processed products is calculated.

[0078] In this embodiment, step S4 uses an image segmentation algorithm to perform pore segmentation based on the three-dimensional data, and calculates the porosity of the raw mother-of-pearl product and each of the processed products, which specifically includes the following steps.

[0079] Step S41: Extracting a pore-matrix binary three-dimensional structural model based on the three-dimensional data using an image segmentation algorithm, wherein the image segmentation algorithm is an Otsu threshold segmentation algorithm or an image segmentation algorithm based on a U-Net deep learning model.

[0080] Step S42: Based on the pore-matrix binary three-dimensional structural model, determine the pore volume and total sample volume of the raw mother-of-pearl product and each of the processed products.

[0081] Step S43: Calculate the porosity of the raw mother-of-pearl product and each of the processed products based on the pore volumes of the raw mother-of-pearl product and each of the processed products and the total volume of the sample.

[0082] Step S5: Determine the quality grade of the raw mother-of-pearl product and each of the processed products based on the porosity of the raw mother-of-pearl product and the processed products, taking into account the relationship between porosity, calcination temperature and sample quality.

[0083] This embodiment takes into account the close correlation between porosity, calcination temperature and sample quality. Generally, the higher the calcination temperature of the processed product of raw mother-of-pearl, the higher its porosity, and the higher the corresponding sample quality; the lower the calcination temperature of the processed product of raw mother-of-pearl, the lower its porosity, and the lower the corresponding sample quality. Therefore, this embodiment starts from the perspective of calcination temperature and porosity, and obtains processed products with different degrees of processing by calcining raw mother-of-pearl at various calcination temperatures, and calculates the porosity of the raw mother-of-pearl and each processed product. Therefore, based on the porosity of the raw mother-of-pearl and each processed product and the calcination temperature, combined with the relationship between porosity, calcination temperature and sample quality, the quality grade of the raw mother-of-pearl and each processed product can be non-destructively evaluated.

[0084] In an exemplary embodiment, the quality grades of raw mother-of-pearl and its processed products include high, medium, and low grades. The porosity range corresponding to the high grade is: ε>40%; the calcination temperature range corresponding to the high grade is: T>800°C. The porosity range corresponding to the medium grade is: 5%≤ε≤40%; the calcination temperature range corresponding to the medium grade is: 400°C≤T≤800°C. The porosity range corresponding to the low grade is: ε<5%; the calcination temperature range corresponding to the low grade is: T<400°C. ε is the porosity and T is the calcination temperature.

[0085] In order to make the technical solution of this embodiment clearer, the specific implementation process of the technical solution of this embodiment is described in detail below in the form of examples. The specific implementation steps are as follows.

[0086] (1) Raw mother-of-pearl and calcined processed products.

[0087] In this embodiment, the raw pearl product is selected from the pearl oyster family Pinctada martensii Pteria martensii Dunker shells, cleaned and crushed, were used as raw material for the experiment. The polished raw mother-of-pearl was then placed in a KSW-6-12ASP integrated box-type resistance furnace for calcination in air at a heating rate of 10°C / min. According to the Pharmacopoeia of the People's Republic of China and the requirements of thermogravimetric analysis (TG) experiments, the temperature was programmed from room temperature to 400°C, 600°C, and 800°C. After 1 hour, the shells were removed from the oven and cooled in a desiccator. Finally, the processed products, calcined at 400°C, 600°C, and 800°C, were obtained, respectively designated MC400, MC600, and MC800.

[0088] (2) Micro-CT scanning.

[0089] This embodiment uses a micro-CT system to carry out X-ray micro-CT experiments, such as Figure 2 As shown, the micro CT system includes an X-ray source 1 for emitting X-rays, and a filter 3, a monochromator 4, a sample stage 5 and an X-ray detector 6 arranged in sequence along the direction of the X-rays.

[0090] In this embodiment, the sample stage 5 is a five-axis precision sample stage with five-dimensional movement directions, which includes a swing table and a rotating table arranged above the swing table. Its movement directions include the left and right dimension, the up and down (lifting) dimension, the pitch swing dimension, the left and right swing dimension and the rotation dimension of the rotating table.

[0091] In this embodiment, the optimal experimental parameters for the micro-CT system when performing an X-ray micro-CT experiment are obtained through theory and experiments. In this embodiment, the X-ray micro-CT experiment was carried out at Shanghai Funa Scientific Instrument Co., Ltd., and the optimal experimental parameters for the X-ray micro-CT experiment were ultimately determined to be: an X-ray energy of 75-85 keV, an X-ray detector 6 using a CCD (Charge Coupled Device) with an effective pixel size of 25 μm, an X-ray single projection exposure time of 500 ms, and a SOD (the distance from the sample to be tested to the X-ray detector 6) set to 12 mm. Specifically, the scanning voltage of the raw mother-of-pearl product is 75kV, the exposure time is 330ms, the scanning average number is 8, the SOD is 12.26mm, the scanning time is 86min, and the scanning pixel is 2.5μm; the scanning voltage of MC400 is 84kV, the exposure time is 606ms, the scanning average number is 8, the SOD is 12.26mm, the scanning time is 103min, and the scanning pixel is 2.5μm; the scanning voltage of MC600 is 84kV, the exposure time is 606ms, the scanning average number is 10, the SOD is 12.26mm, the scanning time is 126min, and the scanning pixel is 2.5μm; the scanning voltage of MC800 is 75kV, the exposure time is 330ms, the scanning average number is 6, the SOD is 12.26mm, the scanning time is 69min, and the scanning pixel is 2.5μm.

[0092] During X-ray micro-CT experiments, projection images are acquired according to a standardized procedure: Samples (raw mother-of-pearl and various processed products) are precisely mounted on the five-axis precision specimen stage of the micro-CT system and rotated 180° around the vertical axis at a constant speed. A microfocus X-ray source (voltage 30-100 kV, current 50-200 μA) and a high-resolution flat-panel detector (pixel size ≤50 μm) are synchronously triggered, and a uniformly sampled strategy is employed to continuously acquire 2D projection images as a set of projection images. These projection images serve as the raw input for 3D reconstruction, generating isotropic voxel-based 3D data using the FDK algorithm. This data includes submicron-resolution phase-contrast micro-CT 3D reconstructed images and the corresponding 3D voxel matrix. This 3D data characterizes the 3D structure of the raw mother-of-pearl and processed products.

[0093] (3) Image processing of projection images, three-dimensional image reconstruction and porosity calculation.

[0094] The specific process of using projection images for phase recovery and slice reconstruction in this embodiment includes: first, geometric correction and noise filtering are performed on the original projection images to eliminate systematic errors and random noise; then, a phase recovery algorithm is used to extract the phase information of the raw mother-of-pearl and each processed product from the projection images, and the refractive index distribution of the raw mother-of-pearl and each processed product is reconstructed; finally, the phase-enhanced projection data is reconstructed into three-dimensional data of isotropic voxels through the FDK algorithm, including a phase contrast micro-CT three-dimensional reconstructed image with sub-micron resolution and the corresponding three-dimensional voxel matrix, thereby generating a high-resolution three-dimensional tomographic slice image.

[0095] In this embodiment, when quantitatively characterizing pore morphological parameters, an image segmentation algorithm, such as the Otsu algorithm or an image segmentation algorithm based on a U-Net deep learning model, is used to perform threshold segmentation on the three-dimensional tomographic slice image. In this embodiment, CTAn analysis software is used to perform threshold segmentation on the three-dimensional tomographic slice image (three-dimensional image). The Otsu algorithm is used to distinguish between the nacre layer and the pores, and a pore-matrix binary three-dimensional structural model is extracted. Based on the pore-matrix binary three-dimensional structural model, the pore volume and total sample volume of the raw mother-of-pearl and each processed product are obtained. The pore volume and total sample volume of the raw mother-of-pearl and each processed product are then substituted into a porosity calculation formula, and quantitative analysis is performed using the porosity calculation formula to calculate the porosity of the raw mother-of-pearl and each processed product.

[0096] In this example, the pore-matrix binary 3D structural model is a simplified representation system established based on 3D data. It divides the internal structure of raw mother-of-pearl and various processed products into a pore phase (cavity or fluid-filled region) and a matrix phase (solid skeleton). The extraction process includes: first, preprocessing the raw 3D data by noise reduction and grayscale normalization; then, performing image threshold segmentation using the Otsu algorithm or an image segmentation algorithm based on the U-Net deep learning model; and finally, optimizing the quality of the pore-matrix binary 3D structural model through morphological operations and connected domain analysis. This pore-matrix binary three-dimensional structural model directly provides basic data for porosity calculation, including the pore volume (V1) and total sample volume (V2) of raw mother-of-pearl and each processed product. The pore volume (V1) and total sample volume (V2) correspond to the number of voxels marked as pore phase and overall matrix in the pore-matrix binary three-dimensional structural model, respectively. Therefore, by substituting the pore volume (V1) and total sample volume (V2) into the porosity calculation formula, the porosity of raw mother-of-pearl and each processed product can be calculated.

[0097] In this embodiment, porosity is the ratio of pore volume to total sample volume, expressed as a percentage. The porosity calculation formula is:

[0098] ε=V1 / V2×100%;

[0099] Where ε is the porosity, V1 is the pore volume, and V2 is the total volume of the sample.

[0100] The porosity results of raw mother-of-pearl and various processed products calculated in this example are shown in Table 1.

[0101] Table 1 Porosity results of raw mother-of-pearl and various processed products

[0102]

[0103] Table 1 shows that during the calcination of raw mother-of-pearl, the porosity of the pearls exhibits a significant relationship with the calcination temperature and sample quality. Specifically, as the calcination temperature increases from 800°C for raw (uncalcined) mother-of-pearl, the porosity increases from 0.2541% to 45.8760%. This indicates that high-temperature calcination promotes the decomposition of organic components and the reorganization of the mineral structure, resulting in more pores. This is accompanied by a decrease in quality due to the loss of volatile substances, and the porosity is negatively correlated with mass loss. The quality grading system uses porosity as the core indicator, combined with data validation (e.g., correction of outliers) and physicochemical properties (e.g., composition and hygroscopicity). The following quality grading criteria are used: high-grade (e.g., MC800, porosity >40%) indicates sufficient calcination and a crisp texture, which facilitates the release of active ingredients; medium-grade (MC600, porosity 5%-40%) indicates moderate calcination; and low-grade (raw mother-of-pearl and MC400, porosity <5%) indicates insufficient calcination. In practical applications, detailed grading can be carried out based on multiple indicators such as calcium content and appearance to ensure scientificity and practicality.

[0104] Figures 3 to 6 It is a three-dimensional structural diagram obtained by reconstructing the two-dimensional projection images of raw mother-of-pearl and three processed products along the X, Y, and Z axes. The X axis is the cross section, the Y axis is the longitudinal section, and the Z axis is the longitudinal section. Figure 3 This is a schematic diagram of the three-dimensional structure of raw mother-of-pearl. Figure 4 This is a schematic diagram of the three-dimensional structure of raw mother-of-pearl after calcination at 400°C for 1 hour. Figure 5 Schematic diagram of the three-dimensional structure of raw mother-of-pearl after calcination at 600°C for 1 hour. Figure 6 This is a schematic diagram of the three-dimensional structure of raw mother-of-pearl after calcining at 800℃ for 1 hour. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 It can be seen that the higher the calcination temperature, the more and larger the pores in the three-dimensional structure, and the higher the porosity.

[0105] This embodiment proposes a non-destructive evaluation method for the quality of mother-of-pearl based on three-dimensional structural porosity. First, the raw mother-of-pearl is calcined by a bright calcination method to obtain processed products with different degrees of processing. Then, according to the brightness change when X-rays penetrate the raw mother-of-pearl and the processed products with different degrees of processing, the parameters of the micro-CT system during image acquisition are determined. The raw mother-of-pearl and the processed products with different degrees of processing are sequentially subjected to micro-CT scanning to obtain multiple sets of projection images. Then, by analyzing the multi-angle projection data (projection images), the phase recovery algorithm is used to reconstruct the refractive index distribution of the raw mother-of-pearl and the processed products with different degrees of processing. Combined with the iterative reconstruction algorithm, three-dimensional data is finally obtained, including the phase contrast micro-CT three-dimensional reconstructed image and the corresponding three-dimensional image. dimensional voxel matrix; then, based on the above three-dimensional data, an image segmentation algorithm is used to extract a pore-matrix binary three-dimensional structural model. The porosity of the raw mother-of-pearl and its processed products with different degrees of processing is calculated using a pore morphology parameter porosity calculation method, that is, a porosity calculation formula is used to calculate the porosity of the raw mother-of-pearl and its processed products with different degrees of processing, thereby achieving quantitative characterization of the microstructure; finally, based on the porosity of the raw mother-of-pearl and its processed products with different degrees of processing, combined with the relationship between porosity, calcination temperature, and sample quality, the sample quality of the raw mother-of-pearl and its processed products with different degrees of processing is determined. The sample quality represents the processing degree of each processed mother-of-pearl product (sufficient calcination, moderate calcination, insufficient calcination), providing a reference for subsequent quality grade classification. In this embodiment, the three-dimensional microstructure of the raw mother-of-pearl and its processed products is non-destructively obtained by X-ray micro-CT scanning, and the quality of the mother-of-pearl is quantitatively evaluated based on the pore morphology parameter of the three-dimensional microstructure, thereby achieving efficient, accurate, rapid, and non-destructive quality evaluation.

[0106] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity, characterized in that: The non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structural porosity includes: The raw mother-of-pearl was calcined at 400°C, 600°C and 800°C respectively by the open calcination method to obtain a number of processed products with different degrees of processing. Performing micro-CT scanning on the raw mother-of-pearl product and each of the processed products to obtain a plurality of projection images; Based on the plurality of projection images, a phase recovery algorithm and an iterative reconstruction algorithm are used to perform three-dimensional image reconstruction to generate three-dimensional data; wherein, geometric correction and noise filtering are performed on each of the projection images to obtain pre-processed projection images; the pre-processed projection images are used as the projection images to reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products based on the phase recovery algorithm; based on the plurality of projection images, the phase recovery algorithm is used to reconstruct the refractive index distribution of the raw mother-of-pearl product and each of the processed products; based on the refractive index distribution of the raw mother-of-pearl product and each of the processed products, the FDK algorithm is used to perform three-dimensional CT reconstruction to generate three-dimensional data of the raw mother-of-pearl product and each of the processed products; the three-dimensional data includes a phase contrast micro-CT three-dimensional reconstructed image and a corresponding three-dimensional voxel matrix; Based on the three-dimensional data, an image segmentation algorithm is used to perform pore segmentation, and the porosity of the raw mother-of-pearl product and each of the processed products is calculated; wherein, based on the three-dimensional data, an Otsu algorithm or an image segmentation algorithm based on a U-Net deep learning model is used to extract a pore-matrix binary three-dimensional structural model; based on the pore-matrix binary three-dimensional structural model, the pore volume and the total sample volume of the raw mother-of-pearl product and each of the processed products are determined; based on the pore volume and the total sample volume of the raw mother-of-pearl product and each of the processed products, ε=V1 / V2×100% is used to calculate the porosity of the raw mother-of-pearl product and each of the processed products, wherein ε is the porosity, V1 is the pore volume, and V2 is the total sample volume; The pore-matrix binary three-dimensional structural model is a simplified characterization system established based on three-dimensional data, which divides the internal structure of the material of raw mother-of-pearl and each processed product into a pore phase and a matrix phase; the pore phase refers to the cavity or fluid-filled area, and the matrix phase refers to the solid skeleton; the extraction process includes: first, denoising and grayscale normalization preprocessing of the original three-dimensional data, and then using the Otsu algorithm or an image segmentation algorithm based on the U-Net deep learning model to perform threshold segmentation of the image, and finally optimizing the quality of the pore-matrix binary three-dimensional structural model through morphological operations and connected domain analysis. The pore-matrix binary three-dimensional structural model directly provides basic data for porosity calculation, including the pore volume and total sample volume of the raw mother-of-pearl and each processed product, wherein the pore volume and total sample volume correspond to the number of voxels marked as the pore phase and the entire matrix in the pore-matrix binary three-dimensional structural model, respectively, so that the pore volume and total sample volume are substituted into the porosity calculation formula to calculate the porosity of the raw mother-of-pearl and each processed product; According to the porosity of the raw mother-of-pearl and each of the processed products, combined with the relationship between porosity, calcination temperature and sample quality, the quality grade of the raw mother-of-pearl and each of the processed products is determined; the quality grades include high grade, medium grade and low grade; the porosity value range corresponding to the high grade is: ε>40%; the calcination temperature value range corresponding to the high grade is: T>800℃; the porosity value range corresponding to the medium grade is: 5%≤ε≤40%; the calcination temperature value range corresponding to the medium grade is: 400℃≤T≤800℃; the porosity value range corresponding to the low grade is: ε<5%; the calcination temperature value range corresponding to the low grade is: T<400℃; wherein, ε is the porosity and T is the calcination temperature.

2. The non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structure porosity according to claim 1, characterized in that: Micro-CT scanning was performed on the raw mother-of-pearl product and each of the processed products to obtain several projection images, specifically including: determining the micro CT scanning parameters of the micro CT system according to the changes in the brightness of the X-rays when the X-rays penetrate the raw mother-of-pearl product and each of the processed products; Based on the micro-CT scanning parameters, the micro-CT system is used to perform micro-CT scanning on the raw mother-of-pearl product and each of the processed products to obtain projection images of the raw mother-of-pearl product and each of the processed products.

3. The non-destructive evaluation method for mother-of-pearl quality based on three-dimensional structure porosity according to claim 2, characterized in that: The micro-CT system includes an X-ray source for emitting X-rays, and a filter, a monochromator, a sample stage and an X-ray detector arranged in sequence along the direction of the X-rays; The filter is used to filter the X-rays and remove the stray scattered rays; The monochromator is used to adjust the energy of the X-rays; The sample stand is used to fix the raw mother-of-pearl product and each of the processed products; The X-ray detector is used to collect projection images of the raw mother-of-pearl product and each of the processed products.

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