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In order to explore the effect of immersion freezing on fruit texture, Huangguan pear was used as the test material, and different immersion freezing temperature (−20, −40 ℃) and immersion solution (single 30% calcium chloride impregnation solution, 30% calcium chloride+4% trehalose+0.05% polylysine composite impregnation solution). Hardness, the content of pectin and microstructure of tissue cells were determined, and the effect of immersion freezing on the texture characteristics of pear was analyzed. The results showed that the loss of pectin and decomposition of original pectin could be better controlled in the trehalose and polylysine immersion solution group when frozen at −40 ℃ (P

Study on occurrence states of rare metal elements provides basic date and theoretical basis for prospecting, processing and selecting metallurgical process of the rare metal ore. In this paper, niobium-tantalum ore from a granite-pegmatite in Henan Province was analyzed by means of chemical analysis, X-ray diffraction analysis, polarization optical microscope, scanning electron microscopy and energy dispersive spectroscopy, the occurrence states of rare metal elements was discussed. The results showed that niobium and tantalum occur in niobium-tantalum minerals and microlite, mainly exist as independent minerals. In addition, a small quantity of niobium and tantalum occurs in cassiterite and exists as isomorphism. Beryllium occurs in beryl and exists as independent mineral. The recoverable minerals are niobium-tantalum minerals, microlite and beryl. In this deposit, niobium and tantalum are of low grade and complex occurrence state, so it is suggested to recycle niobium and tantalum by gravity separation, strong magnetic separation and shaking table.

ObjectivesThis paper aims to study the free vibration characteristics of complicated shape plate coupled with fluid under elastic boundary conditions. MethodsTo this end, the rectangular domain enveloping the complicated shape plate domain is selected, and the plate displacement is expressed by the improved Fourier series in the rectangular domain. Combined with the Rayleigh integral, the relationship between the plate displacement and the surface sound pressure is established, and the integral formula is transformed into polar coordinates to avoid singularity. Aiming at the problem that it is difficult to obtain the explicit expression of the boundary curve in the variable limit integral in local polar coordinates, the structural boundary curves are treated by "replacing curve with straight" to simplify the Rayleigh integral. Based on the energy principle, a semi analytical method for analyzing the free vibration characteristics of complicated shape plate contacting with water on one side is established. ResultsThe numerical examples of rectangular plate, circular plate and some complicated shape plates are given. Compared with the finite element method and literature results, the convergence and accuracy of the method are verified, and the influence of elastic boundary conditions on the added virtual mass incremental (AVMI) factor of plate is discussed. The AVMI factor of each mode reaches the maximum near the dimensionless displacement spring stiffness of 103. At this time, the structure is relatively most affected by the fluid. ConclusionsThis method has strong adaptability and high calculation efficiency. It reveals the free vibration law of complicated shape plate coupled with fluid, and has certain engineering guiding significance.

ObjectivesDue to the larger length-to-diameter ratio of the stern bearing, it is difficult to reflect its actual operating conditions when simplified to the traditional equivalent model of single-point support. Therefore, the influence of the equivalent form of the stern bearing on the transverse vibration characteristics of the shafting is investigated.MethodsThe improved Fourier series is introduced to describe the lateral vibration displacement of propulsion shafting. Then, the calculation model of lateral vibration performance of propulsion shafting under various equivalent forms, such as single-point support, multi-point support or continuous distributed support, are constructed based on the energy principle. Thereby, the influence of the change of support stiffness equivalent to the liquid film pressure on the lateral vibration of the shafting and the influence of the propeller excitation on the vibration response of the shafting are further analyzed. Finally, the results acquired by the proposed model is compared with the results of related references and finite element method (FEM) to verify the validity of the calculation model.ResultsThe multi-point support calculation results converge to the continuous distributed support calculation results. The three-point support equivalent form can be used to study the influence of liquid film pressure distribution on the lateral vibration characteristics of the propulsion shafting. The shafting response under propeller excitation is affected by the revolution speed.Conclusions The research indicates that three-point support equivalent form can be used to analyze the influence of liquid film pressure on the shafting lateral vibration performance. The proposed model in this paper has advantages of good convergence, high accuracy, and less cost-consuming.

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For any positive integer n, the famous Smarandache dual function s* (n) was defined as the greatest positive integer m such that m! |n. The solutions of the equation ... = ω(n)Ω(n) were studied by using the elementary method and to obtain all its positive integer solutions. [ABSTRACT FROM AUTHOR]