Multi-angle phased array ultrasonic technology has important application value in fatigue crack detection of complex structural parts. In this paper, the basic principle of the technique is summarized first, and then the main difficulties in fatigue crack detection of complex structural parts are analyzed, including complex geometric structure interference, quantitative crack characteristics evaluation and environmental factors. To address these challenges, innovative solutions such as deep learning signal processing, multi-parameter feature extraction and adaptive detection strategies are proposed. This study provides a new idea and direction for the further development of fatigue crack detection technology for complex structural parts.

Objective Explore the method of using gas-phase molecularabsorption spectroscopy to determine the ammonia content in unorganizedexhaust gas emissions. Methods Explore the detection method from theaspects of detection limit, calibration curve, precision and accuracy,and compare it with the national standard method. Results Theexperimental results showed that there was a good linear relationshipbetween ammonia concentration and absorbance within the range of $0 \sim 2\mathrm{{mg}}/\mathrm{L}$ , with acorrelation coefficient of 0.9999 . The detection limit of the methodwas ${0.1}\mathrm{{\mug}}/{10}\mathrm{\;{mL}}$ . By measuring the standard sample andconducting spiked recovery tests on the actual sample, the relativestandard deviation RSD of the experimental results was ${0.3}\%\sim {1.5}\%$ , the relative errorwas $-{0.1}\%\sim {0.6}\%$ , and thespiked recovery rate was ${97.1}\%\sim {99.5}\%$ . Compared with thenational standard method, there is no significant difference in theresults obtained by this method. Conclusion This method does not requirepre-treatment, does not use highly toxic reagents, has stronganti-interference ability, and can accurately detect the content ofammonia in the unorganized discharge sample. Suitable for determiningthe ammonia content in unorganized emission samples

Objective In this paper, aiming at the shortcomings of the industry standard of GA/T 1522-2018 Forensic Science Shooting Residue Inspection Scanning Electron Microscopy/X-Ray Spectroscopy, which only provides a few reference characteristic forms and has limited reference such as no reference energy spectrum diagram. Through simulation experiments, a practical reference is provided for the inspection of shooting residues. Methods Taking the shooting of 7.62 mm Type 51 bullet with Type 54 pistol as an example, shooting experiments of naked and clothed human bodies were simulated, and the collection, preparation and inspection steps of shooting residues, typical morphology and composition characteristics of shooting residues were explained in detail. Results Through simulation experiments, the scanning electron microscope morphology and energy spectrum characteristics of the shooting residues produced by the Type 54 pistol shooting the 7.62 mm Type 51 bullet were obtained. Conclusion Each gun and bullet combination has its own specific SEM morphology and energy spectrum characteristics.

Objective Collect peanuts and soybeans in Beijing throughvarious channels, determine the content of 26 metal elements among them.Methods The sample is pre-processed by using a microwave to eliminatethe sample, the content of 26 metal elements was determined by inductivecoupling plasma body constituent. Results The detection limit and linearrange of 26 elements can meet the detection requirements, thecorrelation coefficients are above 0.9980 or more, relative standarddeviation (RSD) in the range of 1.1% to 6.8%, the average recovery rateis within the range of 88.8% to 108.7%. In general the content of $\mathrm{K}$ , Ca, and $\mathrm{{Fe}}$ in soybeans far exceedspeanuts, Al in ordinary soybeans is significantly higher than organicsoybeans, the $\mathrm{{Fe}}$ of redpeanut peanuts is higher than white peanut peanuts. $\mathrm{{Pb}},\mathrm{{Cd}},\mathrm{{Cr}}$ with national standards of food safety have not exceeded the standard.Conclusion Through this method, it can be effectively used for themeasurement of 26 metal elements in peanuts and soybeans.

Objective To evaluate of uncertainty in the determination of residual cyclopropamide in animal food by high-performance liquid chromatography. Methods The sample was repeatedly extracted by the mixture of Trichloroacetic acid and acetonitrile. The supernatant was degreased with n-hexane, and then concentrated by rotating evaporation in a water bath. The mixture of trichloroacetic acid and acetonitrile was redissolved, and then purified by a mixed cation exchange solid phase extraction column. After separation by an amino chromatographic column, acetonitrile water was used as the mobile phase for isocratic elution. The residue of cyclopromazine in animal food was quantitatively determined by diode array detector and external standard method. According to the JJF 1135-2005 Chemical Analysis Measurement Uncertainty Assessment and JJF 1059.1-2012 Measurement Uncertainty Assessment and Representation, the uncertaintygenerated during the entiretesting process includes weighing, standard, standard working curve formulation, standard curve fitting, sample measurement repeatability, instrument and standard recovery rate, and the uncertainty introduced by each factor is calculated, and finally theexpansionuncertainty is obtained. Results When the detection result of cyromazine in chicken was 19.8 µg/kg, with an expanded uncertainty of 3.2 µg/kg. Conclusion The main factors affecting uncertainty are the determination of standard, samples, the preparation of standard curves and the fitting of standard curves.

Under the new circumstances of rapid social and economic development in China, higher education is experiencing significant growth. The government is increasingly emphasizing the importance of laboratory safety in science and engineering universities. Given the significant roles of university laboratories in teaching and research, laboratory safety is characterized by diversification, complexity, and specialization. This paper analyzes the main challenges faced by safety management in engineering university laboratories and proposes improvement measures from four perspectives: strengthening and refining the laboratory safety management responsibility system, timely revision of safety-related documents, promoting safety awareness and education, intensifying laboratory safety inspections, establishing a laboratory safety management information system. These measures aim to enhance the overall level of laboratory safety management, providing solid support for the safe operation of laboratories and facilitating teaching and research activities.

In view of the current situation of laboratory management in local colleges and universities, in order to realize the reform of informatization of laboratory management system in local colleges and universities, it is proposed to build a lightweight laboratory information sharing platform. This paper analyzes the operation characteristics and existing problems of laboratories in local colleges and universities, and discusses the application value of information technology in laboratory management. On this basis, a low-cost and lightweight information sharing platform is constructed. Combined with the current difficulties of laboratory management in institutions, the platform is divided into four basic modules of instruments and equipment, reagents and consumables, users and information push for construction, in order to enhance the transparency and sharing efficiency of laboratory information and improve the laboratory management mode in local institutions.

The issue of food quality and safety is a major issue related to the national economy and people's livelihood, and it is also a livelihood issue that the Chinese people are increasingly concerned about. Grain collection and storage enterprises shall establish a quality and safety traceability system to record and save food quality and safety information objectively, effectively and truly. This article aimed to understand the construction and operation status of the traceability system for grain storage enterprises through on-site research, document review, and conference communication. On the basis of drawing on the experience of traceability systems for grain storage enterprises at home and abroad, and in accordance with relevant laws, regulations, and standards such as the Food safety law of the People's Republic of China, the Opinions of the General Office of the State Council on Accelerating the Construction of Important Product Traceability Systems (State Council Office [2015] No.95), and the Opinions of the Food and Drug Administration on Promoting the Improvement of Traceability Systems for Food and Drug Manufacturers and Operators (Food and Drug Administration [2016] No.122), a quality and safety traceability system for grain storage enterprises was formulated, so as torealize the traceability of grain quality and safety in the forward direction, traceability in the reverse direction, and risk control. When quality and safety problems occur, products could be recalled, the causes could be investigated, and responsibilities could be pursued. Intended to provide reference suggestions for improving the quality and safety traceability system construction of grain storage enterprises, to ensure grain quality and safety, and to provide support for supervision.

Objective To establish a new liquid chromatographic methodfor caffeine content in milk tea, to detect the caffeine content ofinstant milk tea in the region, and to make recommendations on healtheffects. Methods The determination was carried out on a Waters highperformance liquid chromatography Symmetry C18 column $\left({{5\mu}\mathrm{m}\times {150}\mathrm{\;{mm}}\times {4.6}\mathrm{\;{mm}}}\right)$ ,the mobile phase was methanol-water $\left({{30}+ {70}}\right)$ at a flow rateof $1\mathrm{\;{mL}}/\mathrm{{min}}$ ,the detection wavelength of ${272}\mathrm{\;{nm}}$ , and the columntemperature was ${35}^{\circ }\mathrm{C}$ . Results Thecorrelation coefficient was $\mathrm{r}={0.9999}$ over the linear range of 1-30 μg/mL, the recoverieswere 97.2%-99.5%, and the method precision was ${0.54}\%$ . Conclusion The method adoptspotassiun ferrocyanide and zinc acetate precipitation centrifugation,which can rapidly extract the effective components of caffeine in milktea and remove the interference of proteins, shorten the pretreatmenttime, optimize the chromatographic conditions, and accelerate thedetection of caffeine.

Objective A method for the determination of fluoride ion incoalmine water was established by ion chromatography. Methods The watersamples were determined by ${0.22\mu}\mathrm{m}$ qeuosystem filter membrane with a volume of ${25\mu }\mathrm{L}$ . In ion chromatograpy,the determination of fluoride was completed within $4\mathrm{\;{min}}$ under the anionexchange chromatography of HS-5A-P3 with column temperature at ${35}^{\circ }\mathrm{C}$ , eluted with ${20}\mathrm{{mmol}}/\mathrm{L}\mathrm{{KOH}}$ solution at the rate of ${1.0}\mathrm{\;{mL}}/\mathrm{{min}}$ . Results The linear relation between peak area and concentration offluoride were good. The linear return equation was $\mathrm{y}= {30.26}\mathrm{x}- {0.104}$ .The correlation coefficient of the standard curve was above 0.9997 . Thedetection limit was ${0.002}\mathrm{{mg}}/\mathrm{L}$ . Therecovery of fluoride was ${88.0}\%$ -115.5%. The mean value offluorine ion content in the standard sample was within the range of itsguaranteed concentration. Conclusion Compared fluoride ion selectiveelectrode method, the method has the advantages of small sample amountand can be used to determine other components simultaneously. It issuitable for the determination of fluorine ion content in largequantities of coal mine water.