The wave propagation in elastic solids covered by a thin layer has received significant attention due to the existence of Sezawa waves in many applications such as medical imaging. With a Helmholtz decomposition in cylindrical coordinates and subsequent solutions with Bessel functions, it is found that the velocity of such Sezawa waves is the same as the one in Cartesian coordinates, but the displacement will be decaying along the radius with eventual conversion to plane waves. The decaying with radius exhibits a strong contrast to the uniform displacement in the Cartesian formulation, and the asymptotic approximation is accurate in the range about one wavelength away from the origin. The displacement components in the vicinity of origin are naturally given in Bessel functions which can be singular, making it more suitable to analyze waves excited by a point source with solutions from cylindrical coordinates. This is particularly important in extracting vital wave properties and reconstructing the waveform in the vicinity of source of excitation with measurement data from the outer region.

In order to study the wear law of the centrifugal pump flowing surface under different wear-rings clearance, the McLaury wear model was used to conduct the full-passage numerical simulation of solid-liquid two-phase flow in a single-stage single-suction centrifugal pump. The reliability of the numerical calculation method is verified by comparing the experimental data and numerical simulation results. The clearance is 0.1, 0.15, 0.2, 0.3 and 0.5 mm, respectively. The results show that the wear of the centrifugal pump blades is mainly concentrated in the end part and the inlet part of the blade, and the wear of the pressure surface at the end of the suction surface and the front of the blade is more serious. As the clearance increases, the maximum wear value in the impeller increases first and then decreases, reaching a maximum at 0.15 mm. With the increase of the clearance, the wear degree and the wear rate of the volute wall surface first increase and then decrease, and reach the maximum at 0.2 mm. With the increase of the clearance and the concentration of the fluid medium, the wear at the clearance of the centrifugal pump is more serious, and the severe wear area exhibits a point-like circumferential distribution.

Design of digital teaching platform of the Internet of Things (IOT) is to solve the technical problem about how to provide all-digital, high-simulation and feature-rich digital teaching platform of IOT. This design includes the operating terminal, the master node of IOT, slave node of IOT, RFID Read/Write modules and RFID labels. Compared with the existing technology, this design can simulate the operation and usage of IOT in various application environments, it is very convenient for students to study and master the basic technology of IOT, it can be widely used in all kinds of school teaching and scientific research.

Aim at leave examination and approval requirements of digitization and networking, we use J.Office cooperative office platform as developing platform of design and implementation of network leave examination and approval system of CRP digital campus network information platform (CRP), we use leave examination and approval process of Hainan Vocational College of Political Science and Law as an example to give specific implementation steps and demo about network leave examination and approval system.

This paper gives a teaching resources platform that is a comprehensive feature rich, convenient use, strong interactivity based on cloud computing technology. Platform includes various cloud functions and cloud spaces such as identity authentication function, single sign-on function, resources upload/download function, resources collection function, resource integration function, instant communication function, teacher resource cloud space, student resources cloud space, theme resources cloud space, department resources cloud space and schools resources cloud space. Compared with available technology, we can build an no capacity constraints cloud platform for storage and sharing of teaching resources based on the cloud computing technology, this teaching resources cloud platform is an open, interactive public service platform of educational resources.