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Generally, non-destructive testing methods based on the fast neutron technology, such as the associated alpha particle detection technology, can detect hidden hazardous materials without affecting the detected object. The effective neutrons are labeled by recoil alpha particles produced in a D-T reaction, which can significantly improve the signal-to-noise ratio of neutron detection. Meanwhile, the spatial information of the detected object can be obtained based on the spatial resolution of alpha particles. Therefore, neutron detection methods based on accompanying alpha particles have important application prospects in the field of security inspection. The principle and system composition of the neutron detection method based on associated alpha particles are briefly introduced herein. Then, key components of the detection system, such as the neutron tube, alpha particle detector, and gamma detector, are described. Next, the associated alpha particle neutron detection system, which is being studied worldwide, and its progress are presented. Finally, the prospects of this detection method are discussed.

In recent years, widely used hash algorithms such as MD5 and SHA-1 have been found to have varying degrees of security risks.The iterative structure of the SHA-2 algorithm is similar to that of SHA-1, making it vulnerable to attacks as well.Meanwhile, SHA-3 has a complex internal structure and low implementation efficiency.To address these issues, a keyed hash function was designed and implemented based on chaotic neural network and C-MD structure.The approach involved improving the Merkle-Damgard structure by proposing the chaotic neural network Merkle-Damgard (C-MD) structure.This structure can be used to design a hash function that can withstand attacks such as the middle attack, multiple collision attack, and second pre-image attack for long information.Besides, the chaotic neural network was used as the compression function to increase the complexity of the hash function and improve its collision resistance, while also enabling it to output multiple lengths.Moreover, a plaintext preprocessor was designed, which used the coupled image lattice to generate chaos sequence related to the length of the plaintext to fill the plaintext, thus enhancing the ability of the hash function to resist length expansion attacks.Simulation results demonstrate that the proposed hash function performs faster than SHA-2, SHA-3 and the same type of chaotic hash function proposed by Teh et al.It can resist second pre-image attack, multi-collision attack and differential attack, while also exhibiting better collision resistance and mapping uniformity.In addition, the proposed Hash function can output Hash values of different lengths, making it suitable for use in digital signature, key generation, Hash-based message authentication code, deterministic random bit generator, and other application fields.

ObjectiveTo prepare pesticide residues in fruit matrix samples that meet the requirements of homogeneity and stability for the proficiency test.MethodsThe pollution-free apple was selected as the main raw material to prepare the pesticide residue proficiency test samples of myclobutanil and procymidone， and to evaluate the homogeneity and stability. The results of the proficiency test were assessed using robust analysis and Ζ value.ResultsThe homogeneity and stability of the reference materials met the relevant requirements. Among 109 laboratories participated in the proficiency testing， 107 （98.2%） laboratories had satisfactory results. Suspicious test results were reported only in two laboratories， one laboratory for each of the two assessment items.ConclusionAn apple powder matrix sample with pesticide residues is successfully prepared for proficiency test， and could provide an evaluation tool for pesticide residue testing laboratories.

ObjectiveTo establish a method for determination of 12 polar pesticide residues in vegetables and fruits by supercritical fluid chromatography­Q­Orbitrap （SFC­Q­Orbitrap）.MethodsThe samples were extracted with 1% acidified methanol，and the extract was purified by dispersed solid phase extraction， separated by ultra silica column （150 mm× 2.1 mm， 3 μm） and obelisc r column （150 mm× 2.1 mm， 5 μm）， determined by SFC­Q­Orbitrap， scanned by segmented mixed product ions， and quantified by isotope internal standard calibration curve.ResultsThe calibration curves for 12 pesticides exhibited good linearity in the range of 20.0­500 μg/L， with the correlation coefficients（R2） above 0.997. The average recoveries at 0.05 and 0.20 mg/kg spiked levels were in the range of 80.2%­120% and the relative standard deviations （RSD，n＝6） were in the range of 2.14%­14.6%. The limits of detection and the limits of quantification were 0.010 1­0.016 2 mg/kg and 0.050 mg/kg.ConclusionThe method has the advantages of simple operation， accurate quantification and high efficiency. It can meet the requirements determination of high polar pesticide residues in vegetables and fruits.

ObjectiveTo prepare a vegetable matrix reference material with pesticide residues and organize a proficiency testing to assess the performance of domestic laboratories on the quantification of pesticide residues.MethodsThrough simulated field planting, chili sprayed with carbofuran and dimethomorph was used as raw materials to prepare chili matrix reference material with pesticide residues. After preparation, the related evaluation and proficiency testing were carried out. Assigned values were obtained from consensus values by robust analysis and the result were assessed using Z-scores.ResultsThe reference material was assessed to be sufficiently homogeneous and stable (all P >0.05). A total of 155 laboratories, from 30 regions in China participated the proficiency testing, while 142 (91.6%), 5 (3.2%) and 8 (5.2%) laboratories had acceptable performance (|z|≤2.0), warning signal (2.0

There are many influencing factors of bubble curtain clipping technology. In order to obtain the optimal combination of bubble curtain in engineering applications, AUTODYN software was used to design a three factor and three level orthogonal test. The average reduction rate of shock wave peak pressure was used as an evaluation index to study the influence and sensitivity of the number of bubble curtain layers, the burst distance of the bubble curtain and the charge depth on the bubble curtain clipping effect. The results indicate that the clipping ability of the bubble curtain has a great value, and there will be a negative effect if the number of bubble curtain layers continues to increase. The number of bubble curtain layers has the greatest effect on the clipping ability, followed by the charge depth, and the effect of bubble curtain explosion center distance is the smallest. The smaller the burst center distance and the greater the depth of the packet, the better the bubble curtain chipping effect. When the number of bubble curtain layers is 2, the bubble curtain burst distance is 1 m, and the charge depth is 10.5 m, the clipping effect is the best. [ABSTRACT FROM AUTHOR]

The existing high-speed railway operation monitoring data management system consists of four main components, which are data processing, result transfer, visual display and report output. The system has disadvantages including weak visualization and data mining, and lacks of the integration with geology information. Based on the fact, a system architecture was built by using the B/ S mode, which included data layer, service layer, and presentation layer, for storage, distribution, and display of operation monitoring data. The architecture achieved front-end and back-end separation using the ASP. NET and Vue. js framework. Aiming to enhance the system's GIS map visualization and spatial analysis capabilities, the highspeed railway operation monitoring data management system incorporated with the Openlayers which enabled maintenance of monitoring results from multiple data sources, information mining of monitoring data, and visualization of results. The system's effectiveness was verified through application cases involving two operational monitoring projects, covering a total distance of 300 km and comprising 17 061 monitoring points with 11 periods of monitoring data. The research results demonstrate that the system has effectively improved data storage efficiency through pre-entry of points and the combination and import of multiple coordinate systems. The availability of multiple statistical charts, such as the one map module and deformation curve, enriches the display of results and can serve as an effective tool for railway management and maintenance departments in handling high-speed railway monitoring data. [ABSTRACT FROM AUTHOR]