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During the operation of the mine scraper conveyor, it is easy to be affected by the uneven movement of hydraulic support and the uneven cutting bottom of shearer, bearing various types of impact, of which the impact in the vertical direction is the most obvious. This phenomenon will lead to serious wear of the transmission system and unbalanced power of the driving motor. In this article, the formation mechanism of vertical impact of scraper conveyor is studied and the running resistance of the scraper conveyor under different vertical impact effects is calculated. The vertical impact simulation model of the scraper conveyor transmission system is established. The load conditions of scraper conveyor under different working conditions of middle slot clearance, convex and concave of middle slot are simulated and analyzed. The simulation results show that when the middle slot clearance increases, the impact between the middle groove and the middle plate will be stronger, and the impact on the drive system of the scraper conveyor will be more obvious. The peak value of load current produced by vertical impact is positively correlated with the degree of concave or convex bending of the middle groove. The maximum bending angle of adjacent middle slots is the main factor determining the sudden peak value of impact load and the load increment after impact stability of scraper conveyor. The impact caused by the convex and concave bending of the middle groove has a maximum impact on the running resistance of about 12%, which is the main factor affecting the motor power imbalance of the drive system. In the coal mining face, the impact load monitoring platform of scraper conveyor is built, and some impact load monitoring experiments under different vertical bending angles are carried out. The comparison results show that different degrees of vertical impact make the load current fluctuate obviously, and in a short time, the peak value of the impact current can reach 1.5 times of the normal working current, causing serious damage to the chain, motor and other parts of the scraper conveyor. The change trend of the motor current curve after impact is basically consistent with the simulation curve, and the average absolute error range is about 0.435A ~ 1.342A, which verifies the correctness and rationality of the vertical impact simulation model of the scraper conveyor. The research results provide a theoretical basis for improving the intelligent control level of scraper conveyor and ensuring the load stability and power balance of coal mine transportation equipment, so as to reduce the transportation cost of fully mechanized mining face and prolong the service life of transportation equipment.

Scraper conveyor is the core transportation equipment of the fully mechanized working face. Accurately perceiving its form is an important prerequisite to enhance its carrying capacity, alleviate the transmission impact, and improve the straightness of fully mechanized working face. The commonly used indirect measurement methods for the shape of scraper conveyors are difficult to accurately characterize their shape, resulting in significant measurement model errors. To address this issue, an inertial measurement unit is used to directly measure the original pose information of the middle trough of scraper conveyor, achieving accurate acquisition of the shape data of scraper conveyor. A wavelet thresholding denoising method that combines Heursure threshold rules and a new threshold function is used to filter out noise interference in the acceleration signal of the middle trough. Based on this, the motion features of the middle trough are analyzed, and a middle trough motion state recognition model based on random forest algorithm is designed. Based on the motion state recognition results, different strategies are used to update the position of the middle trough. It reduces the accumulated IMU data error over time and improves the precision of IMU position calculation. The improved Harris hawk optimization (HHO) algorithm unscented Kalman filter (UKF) is designed for middle trough attitude calculation. It is verified through experiments that the attitude angle calculated by this method meets the requirements of middle trough attitude measurement. The experimental platform for shape monitoring of scraper conveyors is constructed. It conducts experimental verification on the shape calculation method of scraper conveyors based on motion state recognition and improved HHO optimized UKF. The results show that when the scraper conveyor performs a single sliding with a step distance of 250 mm, the maximum cumulative errors of displacement in the X and Y directions of the scraper conveyor composed of 10 middle troughs are 6.4 mm and 8.4 mm respectively under the horizontal working condition of bottom plate. It remains unchanged in the Z direction. The maximum cumulative errors of pitch angle, roll angle, and heading angle are −0.148°, −0.035°, and 0.457° respectively. Under the working condition of floor undulation, the maximum cumulative errors of displacement in the X, Y, and Z directions are 6.6 mm, 11.5 mm, and 6.9 mm respectively. The maximum cumulative errors of pitch angle, roll angle, and heading angle are −0.540°, −0.157°, and 0.817° respectively. This method can effectively suppress cumulative errors, reduce measurement errors, and achieve accurate perception of the shape of the scraper conveyor.

Objective: This study focused on the analysis and evaluation of the differences in the chemical composition of onions from different origins. Methods: Onions from two main production areas in North and South China （Yunnan and Heilongjiang） were used as raw materials, and the differences in chemical composition content and characteristic chemical composition prostaglandin A1 between the two production areas were analyzed by ultra-high performance liquid chromatography （UHPLC） combined with multivariate statistics. Results: A total of 73 peaks were identified by UHPLC, and the chemical contents of onions from two origins could be distinguished by orthogonal partial least square discriminant analysis （OPLS-DA）, combined with VIP values ＞ 1, P ＜ 0.05 and S-plot. 0.05 and S-plot analysis, and a total of 11 major markers of variation were screened. The PGA1 content of Yunnan onion [(197.21±63.22) mg/kg] was significantly higher than that of Heilongjiang onion [（121.37±43.12) mg/kg]. Conclusion: There were significant differences in the chemical composition content and PGA1 content of onion between the two origins in Yunnan and Heilongjiang.

The current intelligent shearer has the functions of three-dimensional positioning, memory cutting and remote monitoring, but it lacks the detection and early warning protection function of personnel entering the shearer operation area by mistake. Therefore, the precise detection of personnel is one of the key problems to be solved urgently. Affected by the low illumination and complex working conditions of fully mechanized working face, the application of active anti-collision warning technology for coal mine electromechanical equipment based on laser, radio frequency, ultrasonic and other sensors is limited, and the anti-collision technology based on visible light sensor cannot meet the requirements of accuracy and stability. The system architecture of precise detection of personnel in shearer operation area based on infrared thermal imaging technology is built, and then the precise detection method of personnel is proposed. Aiming at the high intensity and uneven characteristics of the infrared image noise in fully mechanized working face, an improved multi-layer guided filter model based on Gauss mask-code is used to filter out infrared image noise effectively and retain the edge information. The moving foreground target motion information under dynamic background is extracted by optical flow method that based on Lucas-Kanade. The intuitionistic fuzzy C-means clustering algorithm based on the weight of local image information is used to segment the infrared image information of the shearer operation area so as to obtain the position information of the moving target. Based on the morphological weighted voting method, the extraction results of the moving target motion information and the infrared image information segmentation results are fused to realize the precise detection of personnel in the shearer operation area. The underground industrial test is carried out in 21208 fully mechanized working face of Gengcun Coal Mine. The results show that the average tracking deviation of the precise detection method for personnel in the shearer operation area is 0.106 5 pixel, the average overlap ratio is 96.10%, and the average single processing time is 0.490 8 s, which meet the needs of field application.

Objective To screen the influencing factors of liver cirrhosis with spontaneous bacterial peritonitis (SBP) so as to establish and verify a diagnostic model of cirrhosis with SBP. Methods A total of 7 461 patients with liver cirrhosis were collected from 2 Grade-A hospitals in Chongqing (Hospital A and B) between July 2015 and December 2019. According to the occurrence of SBP during hospitalization, they were divided into SBP (n=1 173) and non-SBP (n=6 288) groups. A total of 3 776 patients (70%) from Hospital A were randomly selected as the training set, while the remaining 1 619 patients (30%) and the 2 066 patients from hospital B were subjected as the internal and external validation sets respectively. Univariate and logistic analyses were used to screen variables, and logistic regression, random forest (RF), decision tree (DT) and XGBoost models were subsequently established using the training set. Then, the optimized logistic regression model was built on the basis of the above 4 models. Finally, the 5 models were applied in the internal and external verification sets for evaluating and comparing the diagnostic value of different models for cirrhosis with SBP. Results The machine learning algorithm suggested that the 7 common influencing factors with significance in all models were as follows: decompensation stage (OR=5.354, 95%CI: 3.770-7.803), lymphocyte percentage (OR=0.951, 95%CI: 0.939-0.962), total bilirubin (OR=1.003, 95%CI: 1.002-1.004), abnormal C-reactive protein (OR=1.626, 95%CI: 1.310-2.017), international normalized ratio (OR=1.346, 95%CI: 1.091-1.681), prealbumin (OR=0.990, 95%CI: 0.987-0.993) and model for end stage liver disease (MELD) score (OR=1.038, 95%CI: 1.015-1.063). The AUC of the internal verification of the optimized logistic model was 0.860, with a sensitivity of 0.872 and a specificity of 0.719; while the corresponding values of the external verification were 0.818, 0.662 and 0.812, respectively. Delong test showed that there was no statistical difference in AUC between the optimized logistic regression model and the other models with favorable performance. Conclusion The risk prediction models established by machine learning algorithm for liver cirrhosis complicated with SBP have high diagnostic value. Among them, the optimized logistic regression model has performed well in both internal and external verification, and is able to provide reference for clinical diagnosis of SBP.

Objective To determine the effects of diffuse oxygen inhalation on hypoxia stress, blood oxygen saturation and human metabolic process in migrants in plateau, and to illustrate the anti-hypoxia effect of a new oxygen supply mode and its possible molecular mechanism. Methods Ten workers who had migrated to a plateau at an altitude of 3 540 m for more than 1 year were recruited as the subjects. They were asked to breathe oxygen in a newly developed accommodation cabin with diffuse oxygen supply for 3 consecutive days, 2 h per day. Their physiological indexes, blood routine indexes and plasma metabolic profiles before and after oxygen intake were measured and compared. Results ① The oxygen concentration was (22.85±0.36)% on the first day, (22.52±0.76)% on the second day and (22.57±1.05)% on the third day during the diffusion oxygen inhalation in the accommodation cabin. ②The oxygen saturation level and pulse rate were significantly increased after oxygen inhalation in the subjects (P < 0.01), but there was no significant change in blood pressure (P>0.05). ③ There were 44 metabolites significantly changed (VIP>1, P < 0.05). Among them, 18 metabolites were identified in the positive ion mode and 27 in the negative ion mode. And 4 major metabolic pathways also had significant changes [impact>0.05, -log10(P)>1.3]. Conclusion Oxygen inhalation via diffuse oxygen supply can effectively improve the capacity of cardiopulmonary oxygen supply, and alleviate the impact of hypoxia and cold environment on human metabolism.

A linearized model of frequency measurement for the Free Induction Decay (FID) signal is proposed to increase the Proton Magnetometer (PM) precision. First, the nonlinear model of frequency measurement is set up according to the characteristic of the FID signal. Then, according to the error analysis of the MCFM method, the model is linearized on the condition of precision requirement. Furthermore, to reduce the nonlinear error caused by approximate treatment and the trigger time error caused by the random noise, the Least Squares (LS) method is adopted to estimate the slope of the linearized model, and the frequency to be measured is the inverse of the slope. Finally, a PM Prototype is made to verify the effectiveness of the proposed method. Experimental results show that the precision of frequency measurement is obviously increased if the proposed method is adopted for the noised sine signal. Moreover, the RMSD and the NPSD of magnetic-field measurement are about 0.13 nT and 80 pT/Hz1/2, respectively if the proposed method is adopted by PM, which is better than the comparison method.

Objective To investigate the influencing factors of suspected allergic reactions caused by Xueshuantong Injection, and to provide reference for clinical rational drug use. Methods From June 2015 to February 2019, the medical records of the inpatients with the use of Xueshuantong Injection from 7 hospitals were collected. And 78 patients with suspected allergic reaction to the injection were obtained by prescription sequence analysis. Another 312 subjects sampled at 1:4 ratio of gender, age and inpatient department using propensity score matching were assigned into the control group. Conditional logistic regression was used to analyze the effects of solvent, allergy history, single dose and combination on suspected allergic reaction. Results There were no significant differences in the solvent, allergy history and single dose between the 2 groups (P>0.05). But statistical difference was seen in the combination of some drugs (P < 0.05), such as omeprazole (OR=3.28, P=0.007 6), pantoprazole (OR=3.103, P=0.002 8), mannitol (OR=4.017, P=0.000 4), tranexamic acid (OR=2.895, P=0.016 1), lidocaine (OR=4.401, P=0.001 3) and ambroxol (OR=3.607, P=0.003 6). Combination of the above drugs may increase the risk of allergic reactions. Conclusion The combination of Xueshuantong Injection with omeprazole, pantoprazole, mannitol, tranexamic acid, lidocaine and ambroxol may increase the risk of allergic reactions in the patients

Objective To study the correlation between armed conflicts and malaria epidemic in the countries of central Africa. Methods The number of confirmed malaria cases, time of armed conflicts and number of deaths in armed conflicts were collected form the 7 countries of central Africa from 1997 to 2016, and the geographical situation of armed conflicts was drawn using Geographic Information System (GIS). A linear regression model was used to analyze the relationship between armed conflicts and the number of malaria epidemics. Results GIS analysis showed that Democratic Republic of the Congo had the highest frequency of the armed conflicts. Spearman rank correlation analysis indicated that among the 7 countries in the central Africa, the number of armed conflicts in the Democratic Republic of the Congo was positively correlated with the number of confirmed malaria cases (P < 0.05). Linear regression analysis suggested that the number of confirmed malaria cases in the country was linearly related to the annual number of armed conflicts. Conclusion The number of armed conflicts is clearly associated with the prevalence of malaria in the Democratic Republic of the Congo.

Objective To analyze the factors contributing to heat stroke in troops from different regions on the first day after arrival in Chongqing. Methods Using a self-designed questionnaire, we investigated the daily activities, training, and the occurrence of heat stroke in 2 troops from 2 different regions before and during the transportation and after their arrival at Chongqing. The individuals having heat stroke on the first day of arrival served as the heat stroke group, and those without heat stroke served as the control group for comparison of the data to identify the factors contributing to heat stroke in the 2 troops. Results Twelve (33.3%) individuals in troop A and 16 (48.6%) in troop B had heat stroke on the first day after arrival in Chongqing. In troop A, the volume of daily water intake, sleep time and sleep quality differed significantly between the individuals with heat stroke and those without during the transportation (P < 0.05); In troop B, the weekly training time and the volume of water intake on the first day of arrival differed significantly between the heat stroke and non-heat stroke groups (P < 0.05).Logistic multivariate regression showed that an increased mean daily water intake and improved daily sleep quality during transportation in troop A and a longer weekly training time in troop B were the protective factors against heat stroke. Conclusion The differences in the geographical environment in terms of climate and altitude between the 2 troops resulted in significant differences in the factors affecting the occurrence of heat stroke on the first day after their arrival, suggesting the importance of addressing the geographical differences between the stationing site and the mission site in designing measures for controlling environmentally sensitive diseases for the trans-regional mobile troops.

In supersonic plasma spraying system (SAPS), heat transfer from arc plasma is characterized by several distinct features, such as transport of dissociation and ionization energy and of electrical charges in addition to mass transport. The thermodynamic and transport properties of plasma jet were influenced by several main parameters such as primary gas flow rate, the H2 vol.% and current intensity A. This paper first analyzes the effect of these parameters on the temperature and velocity of plasma jet theoretically. Further, the loading particles were melted and accelerated by plasma jet. Effects of several main parameters such as carrier gas flow rate, the H2 vol.%, the current intensity, the voltage and the spraying distance on temperature and velocity of in-flight particle were studied experimentally. The average maximum temperature and velocity of in-flight particle at any given parameters were systematically quantified. Optimal SAPS process parameters were given in this paper. In general, increasing the particles impacting velocity and surface temperature can improve the maximum spreading factor and decrease the coating porosity.

Through numerical simulation, key issues concerning the plasma jet features as well as the sizes of nozzle for supersonic atmosphere plasma spraying (SAPS) were analyzed in this paper. Numerical results were compared with the experimental measurements and a good agreement has been achieved. Due to the effect of mechanical compression, the increasing sizes of r1, r2, r3 and r4 (r1, r2, r3 and r4 are the sizes of nozzle) lead to a decrease in temperature and velocity of plasma jet. But large size of r5 can increase the external temperature and velocity of plasma jet, which benefit particles accelerating at the far downstream region. A new nozzle was designed based on the simulation results. Compared to the temperature and velocity of plasma jet in the original nozzle, the maximum temperature and velocity of plasma jet in new structure are increased by about 9.8% and 44.5%, which is a benefit to the particles to reach a higher speed and surface temperature.

In order to obtain parameters of running state of shearer accurately, a design scheme of wireless monitoring system of shearer was proposed. The wireless sensor nodes with specific-function are installed on appointed part of shearer frame,which are used to collect working signal of shearer. The signal is real-timely processed by DSP and is transmitted to wireless bridge AP by wireless MESH network, then it is transmitted to center computer by fiber. The working signal of shearer is analyzed by software of the center computer which makes alarming or other processing according to set threshold. The result of actual test showed that the system runs well and the signal intensity of wireless network can meet with requirements of wireless monitoring system of shearer.