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This article presents the smelting practice of 9Ni steel for ultra-low-temperature pressure vessel in a certain steel plant by the "BOF → LF → scraping slag/fetching slag → LF → VD → CC" process. The decarburization and desulfurization in the BOF + LF process require that the steel produced by the converter has a low phosphorus （w［P］） ≤ 0.009%） and carbon content （w［C］） ≤ 0.05%）， with an average desulfurization rate of 74.3% and an average decarburization rate of 51.2%. The control of phosphorus content is more difficult than carbon content in the production process. In the scraping slag process， the average phosphorus reversion rate in the molten steel is 16.89%， while in the fetching slag process， it is 22.61%. Although the scraping slag process results in a lower phosphorus reversion rate in the molten steel， the processing time is increased by 15 to 20 minutes， and the average molten steel loss is increased by 3.1 t per heat. After adjusting the addition of nickel plates from the converter to the ladle furnace， the average nickel recovery rate increases by 3.74%. Through optimizing the production process， the molten steel in the tundish meets internal control requirements for phosphorus（ P）， sulfur （S）， nitrogen N， total oxygen （T.O）， and carbon （C）， ensuring high purity of the molten steel， the macrostructure center segregation of the cast slab reaches 1.0～1.5 grade in class C， the internal and surface quality of the cast slab are good. The rolled steel plate exhibits excellent performance at -196 ℃.

On the basis of centralized structure and distributed structure, the model based on peer-to-peer structure is established. Aimed in the problem of source optimal selection for passive location relative navigation under peer-to-peer structure, the Gauss-Newton method is used to set the initial value of relative navigation Kalman filter to make it converge quickly. With defining time, position, geometry and synthetic error factors, and setting different simulation environments, the influence of distance, speed, time deviation and geometric distribution position on relative navigation accuracy is studied. The simulation results show that the deviation is inversely proportional to the relative navigation accuracy, and the navigation accuracy is the highest when the connecting angle between the node to be located and the navigation source is 90°, the accuracy of the wide baseline scheme is significantly better than that of the narrow baseline scheme when the navigation source is configured linearly, and the accuracy of four-source positioning is better than that of two-source or three-source positioning. The algorithm model established in this paper is able to analyze the influence of different factors on positioning errors.

This paper studied the predation and dispersal of Lithocarps glaber seeds by rodents in the Tiantong National Forest Park (29 degrees 48'N, 121 degrees 47'E) of Ningbo City, Zhejiang Province. Five seeds release transects (three in evergreen broad-leaved forest, one in Pinus messoniana forest, and one in shrub), and two seeds release states (covered/uncovered and tagged/untagged) were set up. Iron snare traps were baited to determine the effects of rodents on seeds disappearance. The results showed that two species of rodents, Niviventer confucianus and N. fulvescensi, were the potential predators and dispersers of the seeds. The lost seeds labeled with small piece of tintags could be classified into three categories, i. e., 1) seeds consumed by rodents, with tags stuck seed fragments; 2) seeds cut off from tags, with tags kept only; and 3) both seeds and tags disappeared. The loss rate of seeds was high at the beginning of the observation, and then decreased gradually. The daily seeds disappearance rate (DS-DR) was variable in different habitats, with the highest (1.03%) in evergreen broad-leaved forest and the lowest (0.32%) in shrub. The proportion of these three categories was different, and related with habitat types. The difference of DSDR between covered and uncovered states was statistically significant (P < 0.05), with a higher DSDR under uncovered state. No significant difference was observed between the DSDR of tagged and untagged. The distance of seeds dispersal by rodents was within 6.7 m.

Five mature plants of Castanopsis fargesii population were randomly chosen to study the spatial and temporal pattern of its seed rain in Tiantong National Forest Park, Zhejiang Province in 2003. The duration of seed rain observed from the five samples was about 45 days, from November 3rd to December 16th, with a distinguishable dropping peak between November 18th and 27th. The average seed rain density estimated from the traps deployed under the crown was 112.8 seeds.m(-2), ranging from 70 to 239.5 seeds.m(-2). Of the total acorns collected by seed traps, the viable accounted for 27.3%, the immature 25.7%, the eaten by rodents 5.0%, and the infected by larvae 42.0%. The acorns on the ground mainly distributed under the parent tree crown within 8 m from the trunk, and the spatial pattern of seed density on the ground fitted the quadratic distribution.