Regularity in distribution, and control, of pests in the hall of mental cultivation, the Forbidden City, Beijing, China

Pests can seriously threaten the safety of organic relics and historic buildings. Every year, the Palace Museum spends a large of money and time preventing and controlling pests, but there is still no a better systematic and targeted method. The Hall of Mental Cultivation is a representative and essential building in the Forbidden City. Through three years of pest monitoring, the species, quantity, and occurrence regularity of the major pests were investigated. During this time, more than ten species of insects were trapped. These included carpet beetles (Anthrenus picturatus hintoni Mroczkowski, 1952 and Thylodrias contractus Motschulsky, 1839), silverfish (Ctenolepisma longicaudata Escherich, 1905), powder-post beetles (Lyctus brunneus Stephens, 1830), booklice (Liposcelis bostrychophila Badonnel, 1931), spider beetles (Ptinus japonicus Reitter, 1877 and Gibbium aequinoctiale Boieldieu, 1865) and the case bearing clothes moths (Tinea pellionella Linnaeus, 1758), among which the Anthrenus picturatus was the primary pests. Abundant resources of organic relics, suitable temperature, humidity, and light environment, and cypress existence are favorable factors for the occurrence of pests, and analysis of these factors is helpful for further integrated pest management (IPM). The period with the most significant number of active pests in the Hall of Mental Cultivation is July and August, and April and May are the rapid growth period. Carpet beetles are the key pests that can affect the overall change trend significantly. It should combine with their living habits, the ideal treatment time and methods, to give them a better control. Fumigation should be done in July and August, while chemical spray should be done referring to the florescence of outdoor trees (March to June), and used of pheromone is reasonable preventative measures.

A prediction method of fire frequency: Based on the optimization of SARIMA model

In the current study, based on the national fire statistics from 2003 to 2017, we analyzed the 24-hour occurrence regularity of fire in China to study the occurrence regularity and influencing factors of fire and provide a reference for scientific and effective fire prevention. The results show that the frequency of fire is low from 0 to 6 at night, accounting for about 13.48%, but the death toll due to fire is relatively high, accounting for about 39.90%. Considering the strong seasonal characteristics of the time series of monthly fire frequency, the SARIMA model predicts the fire frequency. According to the characteristics of time series data and prediction results, an optimized Seasonal Autoregressive Integrated Moving Average Model (SARIMA) model based on Quantile outlier detection method and similar mean interpolation method is proposed, and finally, the optimal model is constructed as SARIMA (1,1,1) (1,1,1) 12 for prediction. The results show that: according to the optimized SARIMA model to predict the number of fires in 2018 and 2019, the root mean square error of the fitting results is 2826.93, which is less than that of the SARIMA model, indicating that the improved SARIMA model has a better fitting effect. The accuracy of the results is increased by 11.5%. These findings verified that the optimized SARIMA model is an effective improvement for the series with quantile outliers, and it is more suitable for the data prediction with seasonal characteristics. The research results can better mine the law of fire aggregation and provide theoretical support for fire prevention and control work of the fire department.

Occurrence Regularity of Silt–Clay Minerals in Wind Eroded Deserts of Northwest China

Wind erosion desertification is the most serious type of land degradation in Northwest China, so it is an important task for ecological management in the region. As the core of ecological management, soil quality is mainly affected by the presence of silt–clay content. Therefore, the grasp of its occurrence regularity is the key to controlling wind erosion desertification. At present, research on silt–clay contents is mainly independent in each local area and lacks integrity, which makes it difficult to meet the overall evaluation and planning requirements. To this end, this paper reviewed the related studies on the occurrence and control of wind erosion desertification in recent years and collected nearly 300 relevant silt–clay content data points. We studied the occurrence regularity of silt–clay content during the occurrence and treatment of wind erosion desertification and revealed the mechanism of silt–clay content in different processes. On this basis, the degree of wind erosion desertification in the major areas of Northwest China in the last five years was evaluated by calculations based on soil typing theory, and the fractal dimension interval (2.41–2.53) for the critical discrimination of desertification in these areas was obtained. The results showed that there were obvious distribution intervals of silt–clay content for different degrees of wind erosion desertification. Qualitative changes in soil quality during degradation ranged from light to moderate wind erosion desertification. The occurrence and control of wind erosion desertification were largely affected by the processes of silt–clay particles loss and aggregation. Among the three main treatment measures, biological measures enhanced silt–clay content most significantly. In this study, the occurrence regularity of silt–clay minerals in wind erosion desertification in Northwest China was revealed as a whole. This study provided a preliminary overall judgement of the dynamic evolution of wind erosion desertification, which provided a reference for the overall evaluation and global governance planning of wind erosion desertification in Northwest China.

Optical experiments of string cavitation in diesel injector tapered nozzles

Flow inside the diesel nozzle is crucial to spray, combustion, and emissions. This work aimed to improve the understanding of effects of internal fuel-flow on diesel spray, especially the special string cavitating flow. Optical experiments were employed for characterizing the formation of string cavitation inside the transparent scaled-up tapered diesel orifices. Simultaneously, the corresponding evolution of spray cone angles were obtained. Results show that there were two origins of the string cavitation, which were originated from inlet and outlet of the orifice, respectively. Moreover, there were two typical development processes of the string cavitation between hole and hole, which were defined as type-A and type-B string cavitation. Furthermore, effects of string cavitation were analyzed: it could trigger the geometry-induced cavitation and make a sharp increase of spray cone angle. Finally, the relationships between the occurrence regularity of string cavitation, the needle lift and the injection pressure were revealed by comparison of different needle lifts and different injection pressures.

A method to remove gas hazard around underground thrust faults: Kilometre directional feathery drilling

In this paper, we take the W2303 working face in Sihe mine, Shanxi Province, China as a project case, where it has been met with three thrust faults. The occurrence regularity of coal gas near the faults are studied, and the gas content around the faults are measured. The comprehensive measures of gas extraction are carried out, including the wear layer and in-seam kilometer directional feathery drilling combined with multi-branch technique. The gas threat around underground thrust faults is effectively eliminated. This technical engineering practice has a good guiding significance to other similar mining areas.