Investigation of COVID-19-related symptoms based on factor analysis.

BACKGROUND: The application of factor analysis in the study of the clinical symptoms of coronavirus disease 2019 (COVID-19) was investigated, to provide a reference for basic research on COVID-19 and its prevention and control. METHODS: The data of 60 patients with COVID-19 in Jingzhou Hospital of Traditional Chinese Medicine and the Second People's Hospital of Longgang District in Shenzhen were extracted using principal component analysis. Factor analysis was used to investigate the factors related to symptoms of COVID-19. Based on the combination of factors, the clinical types of the factors were defined according to our professional knowledge. Factor loadings were calculated, and pairwise correlation analysis of symptoms was performed. RESULTS: Factor analysis showed that the clinical symptoms of COVID-19 cases could be divided into respiratory-digestive, neurological, cough-wheezing, upper respiratory, and digestive symptoms. Pairwise correlation analysis showed that there were a total of eight pairs of symptoms: fever-palpitation, coughexpectoration, expectoration-wheezing, dry mouth-bitter taste in the mouth, poor appetite-fatigue, fatiguedizziness, diarrhea-palpitation, and dizziness-headache. CONCLUSIONS: The symptoms and syndromes of COVID-19 are complex. Respiratory symptoms dominate, and digestive symptoms are also present. Factor analysis is suitable for studying the characteristics of the clinical symptoms of COVID-19, providing a new idea for the comprehensive analysis of clinical symptoms.

[Construction of age group vegetation index and preliminary application].

In the present paper, one remote sensing index-age group vegetation index (AGVI) was put forward, and its feasibility was verified. Taking 518 groups of pine forest age group data collected in 13 counties (cities) of Sanming, Jiangle, Shaxian, Nanping, Huaan, Yunxiao, Nanping, Anxi, Putian, Changting, Jianyang, Ningde and Fuqing, Fujian Province and HJ-1 CCD multi-spectral image at the same time-phase as the basis, the spectrum differences of blue, green, red, near infrared and NDVI of each age group were analyzed, showing the characteristics of young forest>middle-aged forest>over-mature forest>mature forest>near mature forest at near infrared band and mature forest>near mature forest>over-mature forest>young forest>middle-aged forest at NDVI, thus the age group vegetation index (AGVI) was constructed; the index could increase the absolute and relative spectrum differences among age groups. For the pine forest AGVI, cluster analysis was conducted with K-mean method, showing that the division accuracy of pine forest age group was 80.45%, and the accurate rate was 90.41%. Therefore, the effectiveness of age group vegetation index constructed was confirmed.

[Spectral features analysis of Pinus massoniana with pest of Dendrolimus punctatus Walker and levels detection].

Taking 51 field measured hyperspectral data with different pest levels in Yanping, Fujian Province as objects, the spectral reflectance and first derivative features of 4 levels of healthy, mild, moderate and severe insect pest were analyzed. On the basis of 7 detecting parameters construction, the pest level detecting models were built. The results showed that (1) the spectral reflectance of Pinus massoniana with pests were significantly lower than that of healthy state, and the higher the pest level, the lower the reflectance; (2) with the increase in pest level, the spectral reflectance curves' "green peak" and "red valley" of Pinus massoniana gradually disappeared, and the red edge was leveleds (3) the pest led to spectral "green peak" red shift, red edge position blue shift, but the changes in "red valley" and near-infrared position were complicated; (4) CARI, RES, REA and REDVI were highly relevant to pest levels, and the correlations between REP, RERVI, RENDVI and pest level were weak; (5) the multiple linear regression model with the variables of the 7 detection parameters could effectively detect the pest levels of Dendrolimus punctatus Walker, with both the estimation rate and accuracy above 0.85.

[Construction of vegetation shadow index (SVI) and application effects in four remote sensing images].

Taking the images of Landsat TM, ALOS AVNIR-2, CBERS-02B CCD and HJ-1 CCD as the experimental data, for increasing the differences among shaded area, bright area and water further, the present paper construed a novel vegetation index-Shaded Vegetation Index(SVI), which can not only keep the absolute differences among bright area, shaded area and water area in the near-infrared band, but also can enlarge NDVI, eliminate the possible mixes, and change the histogram "skewed" phenomenon of NDVI, so the vegetation index value is closer to normal distribution, and more in line with the filed condition; this new index was applied to the surface features of large difference of the near-infrared radiation characteristics. Verified by accuracy assessment for the bright area, shaded area and water area recognition effects with SVI, it was showed that the overall classification accuracies of these images were up to 98. 89%, 100%, 97.78% and 97.78% respectively, with the overall Kappa statistics of 0.9833, 1, 0.9667, and 0.966 7, indicating that SVI has excellent detection effects for bright area, shaded area and water area; the statistical comparison of sub-images between SVI and NDVI also illustrated the reliability and effectiveness of SVI, which can be applied in the shadow removal for remote sensing images.