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Zhengyan Liang,1 Jinqing Wang,1 Minqiang Zhang,1– 4 Yingshi He,1 Jiaxin Quan,1 Da Yi1 1School of Psychology, South China Normal University, Guangzhou, People’s Republic of China; 2Key Laboratory of Brain, Cognition and Education Sciences, Ministry of Education, Guangzhou, People’s Republic of China; 3Center for Studies of Psychological Application, School of Psychology, Guangzhou, People’s Republic of China; 4Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, People’s Republic of ChinaCorrespondence: Minqiang Zhang, School of Psychology, South China Normal University, No. 55, West of Zhongshan Avenue, Tianhe District, Guangzhou, 510631, People’s Republic of China, Email zhangminqiang@m.scnu.edu.cnIntroduction: There are two types of master’s qualifications in China. One is the academic qualification that pays more attention to academic research, aiming to cultivate research-oriented talents; while the other is the application-oriented qualification that focuses more on practical ability, aiming to cultivate applied-oriented talents. The purpose of this study is to explore the impact of the COVID-19 on the learning activities of postgraduate students, as well as the differences in the extent to which the learning activities of postgraduate students of different qualification types are affected and their mental health status.Methods: A self-constructed scale for the pandemic’s impact on master’s students, the self-rating anxiety scale and the self-rating depression scale were applied in the study. The single- and multi-group latent class analyses were used to investigate the impact of the pandemic on postgraduate students of different qualification types.Results: A total of 2818 responses were collected. The single-group latent class analysis identified four classes. The multi-group latent class analysis showed that no absolute homogeneity existed between different groups. In general, the number of academic master’s students affected was greater than application-oriented master’s students. Application-oriented master’s students were more affected by course activities, while academic master’s students were more affected by academic and social activities. Results show that individuals more affected had higher levels of anxiety and depression. Compared to course activities, impacts on social activities were more likely to cause anxiety and depression.Discussion: Universities can provide a more flexible way of assistance to different qualification types of postgraduate students. Furthermore, social activities play an important role in the mental health of postgraduate students. Therefore, under the background of normalization of pandemic prevention and control, schools should pay more attention to students’ interpersonal communication activities to help relieve students’ anxiety, depression, and other negative emotions.Keywords: COVID-19 pandemic, application-oriented postgraduate students, academic postgraduate students, learning activities, multi-group latent class analysis

The effect of compatibilization on the reciprocating frictional behavior of a polyamide 66 (PA66)/ultra-high molecular weight polyethylene (UHMWPE) blend was investigated. The influence of the amount of added maleic anhydride–grafted polyethylene (MAH-g-HDPE) on the phase morphology, compatibility, and viscoelasticity was explored using scanning electric microscopy (SEM), dynamic mechanical analysis (DMA), and capillary rheometry. In addition, the effect of MAH-g-HDPE on the reciprocating friction and wear performance of the PA66/UHMWPE blend was tested. The worn surface, transfer film, and wear debris were analyzed using SEM, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results showed that the maleic anhydride groups in the MAH-g-HDPE improved the compatibility of PA66 and UHMWPE, and the addition of MAH-g-HDPE enhanced the interface bonding strength and lowered the polar difference between PA and UHMWPE. Therefore, the improved compatibility enh...

Two disputes about the metallographic testing of welding joints of the high alloy steel on-site installation welding of the current power plant boiler are discussed. This thesis analyzes the reasons for the two dispute. On this basis, the accordance for the detection, detection method, qualification assessment standard and the ratio of detected parts to quantity are defined. This paper can provide reference for strengthening the quality of welding joints for high alloy steel installation welding of power station boilers.

The method to establish the pointing model of the 65-meter radio telescope of Shanghai Astronomical Observatory (TM65 m) is described. The single-point data are collected by means of “cross scan”, then, they are fitted with a model including both the Gaussian and nonlinear terms. It is also simulated and analyzed how the antenna beam is broadened in the scanning process because of the angular size of a source. And the orbit prediction of sources is used to improve the modelling efficiency. Finally, an eight-parameter pointing model is built after fitting all the collected single-point errors. It is verified that the model works well in the X band and other low-frequency bands, the pointing accuracy at the X band attains 12.36 arcsec.

The flotation separation of scheelite from calcite using sodium oleate as collector and acidified sodium silicate as depressant has been studied. The results show that sodium oleate has collecting ability to both scheelite and calcite and the flotation separation of scheelite from calcite cannot be realized if collector is used only. The depressant acidified sodium silicate has selective depression effect on calcite and the optimum ratio of sodium silicate to oxalic is 3:1. The use of acidified sodium silicate as depressant can achieve the flotation separation of scheelite from calcite. Infrared studies and zeta potential measurements showed that the pre-adsorption of acidified sodium silicate interferes with the adsorption of sodium oleate on calcite surface while does not interfere with its adsorption on scheelite surface.

At first, the receiving system of the Tianma 65m radio telescope (TM65m in brief) and its noise characteristics at the L, S, C, and X four frequency bands are described. Then, a few measuring methods of system noise temperature are discussed, and the major factors affecting the noise temperature measurement are analyzed, including the errors caused by the non-linearity, feed network insertion loss, mismatch, and so on. With the Y-factor method the noise temperature of the noise source calibrated in the laboratory is verified, indicating that its accuracy attains ∼0.2K. Finally, the system noise temperatures actually measured at the four frequency bands and an analysis on the result are given.

In this study, the relationship of the growth of invasion fish with water eutrophication processes was explored in Yangtze estuary, China. High water ammonia nitrogen concentration produced high effects on the growth and survival of mosquitofish Gambusia affinis. When the ammonia nitrogen was higher than 51.75 mg/l, the fish death rate obviously increased with days, and at the 4th day fish presented the highest mortality, while 23.72 mg/l ammonia nitrogen conditions have been able to ensure fish survival for two days in experiment treatment. Therefore, ammonia nitrogen of Grade V polluted water (national water quality criteria) is just 3 mg/l, and the water can be enough to support fish normal survival. Our results suggest mosquitofish was a suitable pioneer species for restoring polluted water ecology and purify water.

Distribution characteristics of fish assemblages and environmental variation in emerged plant, floating-leaved plant and blank habitats were studied. Emergent plant habitat supported the greatest fish biomass, density and body size, followed by floating-leaved plant habitat, and those of blank habitat was the lowest. Transparency of emergent plant habitat decreased during the period, but of blank habitat increased. Species number of dominant fish of emergent plant habitat compared to the others decreased from four species, i.e., Hemicculter leuciclus, Pseudobrama simoni, Carassius auratus and Ophicephalus argus in May to the single one, C. auratus in September. Those of blank habitat increased from two species, H. leuciclus and Pseudorasbora parva to four species, H. leuciclus, C. auratus, P. parva and O. argus. This result suggested that emergent plant with excessively high density could worsen habitat physical and chemical conditions, resulted in the fish’s emigration to unvegetated area. Those of floating-leaved plant habitat from two species, Cultrichthys erythropterus and P. simoni, changed into four species, C. erythropterus, P. simoni, H. leuciclus and P. parva. The increasing structure complexity and biomass of floating-leaved macrophyte promoted the increase of dominant fish species number with seasonal change. C. auratus, C. erythropterus and H. leuciclus displayed special preferences on emergent plant, floating-leaved plant and blank habitats respectively. Fish’s special habitat preference was determined by plant physical morphology, habitat characteristics and fish breeding habits.

TM65m radio telescope Ku and Ka-band antenna pointing, subreflector model, efficiency, sensitivity, and system noise temperature performance are reported in this paper. The key indicators of radio astronomy receiving system are introduced firstly. Secondly the band measurement essential points are discussed these are point and sub-reflector model construction and atmosphere influence. The antenna efficiency, sensitivity and system noise temperature of the two bands are described finally. The measurement results show that in the Ku and Ka-band, in the middle of the elevation, Ku-band efficiency can be controlled to 60%, Ka-band can be controlled to 38%. And in the higher and lower elevations, there is a significant decline in the efficiency since the main surface deformation.

Zizania latifolia mainly grows in the land/inland water ecotones of river channels and lowland swamps of Lake Taihu Basin.Its growth condition is representative in this area.Four different environment conditions such as implanted ecological filter bed,biological oxidation pond,subsurface flow and surface flow integrated artificial wetland and horizontal subsurface flow artificial wetland have been designed based on the status of land/inland water ecotones of river channels.The growth adaptabilities of Z.latifolia in different environments were studied so as to provide a scientific evidence and technical support for establishment and restoration of the degraded vegetation communities of land/inland water ecotones of river channels.The results showed that Z.latifolia was able to adapt to different growth environments such as zeolite matrix and hydroponics;the growth rate and luxuriance degree differed among substrates.

The mathematical model of spaceborne SAR systems and its computer simulations are described. Results of computer simulations about range migration, range migration correction, asimuth weighting and signal generation/processing are given. This software can be used to simulate the dynamic processes in spaceborne SAR systems, to develop new signal processing techniques and to evaluate the performance of the designed system.

Relations between the zeros of a continuous time system and its sampled version is discussed in this note. It depends on the coefficients and the relative degree of the transfer function. The criterion for ensuring limiting stable sampled system with time delay is presented.