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According to GJB1179A-2012 "Quality Requirements for Low Speed and High Speed Wind Tunnel Flow Fields", the velocity field calibration is a key item in the wind tunnel flow field calibration and an important basis for evaluating whether wind tunnels have the ability to conduct model tests. Center line probe is a universal calibration instrument used for velocity field calibration in the subsonic and transonic wind tunnels. In order to reduce the disturbance of the center line probe on the flow field and generate an undisturbed flow field in the test section, it is generally required that the blockage degree should not exceed 0.5%, and the head cone is located in the contraction section of the wind tunnel. In recent years, with the construction of large-scale transonic wind tunnels of over 2 meters in China, traditional center line probe design schemes face certain difficulties in the manufacturing, installation and calibration. In response to this issue, the aerodynamic shape and installation position of the head of the center line probe is optimized, achieving the weakening of the intensity and disturbance range of the conical shock wave at the head of the probe, and exerting the wave attenuation ability of the acceleration zone in the test section. A non-interference flow field consistent with traditional long center line probe is generated in the test section, greatly shortening the length of the probe. The present study provides a feasible technical solution for the design of center line probe for velocity field calibration in large-scale transonic wind tunnels.

Photocatalytic technology shows significant advantages in environmental remediation and catalysis due to use clean solar energy directly and highly mineralization of pollutants. Metal oxides photocatalysts have the disadvantages of a large band gap and high hole-electron recombination. In recent years，MXene have potential applications in the modification of metal oxide with advantages of good electron transfer ability，environmental stability，rich layer structure and large specific surface area. In this paper，the preparation methods of MXene were firstly outlined，including hydrofluoric acid etching，fluoride etching，alkali etching，hydrochloric acid hydrothermal etching，Lewis acid etching，electrochemical etching，chemical vapor deposition and high temperature decomposition method. Secondly，the surface functional groups，dispersibility and chemical stability were introduced. Then，photocatalytic mechanism of MXene/metal oxide photocatalysts was reviewed，including photocatalytic mechanism of metal oxide，photocatalytic activity enhanced mechanism of MXene/metal oxide. Moreover，applications of MXene/metal oxide photocatalysts were introduced，including the photocatalytic degradation of pharmaceutical and personal care products（PPCPs） and dyes，and the photo-stability. Finally，the existing problems of MXene/metal oxide photocatalysts were prospected，which could provide the theoretical supporting for design of efficient photocatalysts and water treatment applications.

ObjectiveTo investigate beverage consumption and influence factors of primary and secondary school students， and provide a scientific basis for guiding the reasonable consumption of beverages for middle and elementary school students in Hebei Province.MethodsMulti-stage stratified cluster random sampling method was applied to sample participants， and 3 259 primary and secondary school students were enrolled. Food Frequency Questionnaire was employed to collect beverage consumption situation in the last month.ResultsThe beverage consumption rate of primary and secondary school students in Hebei Province was 66.62% （2 171/3 259）. And the most common beverages were： vegetable protein beverages （28.60%）， carbonated beverages （24.70%）， non-100% fruit and vegetable juices （24.09%）. The consumption rates of plant protein beverages， non-100% fruit and vegetable juice beverages， carbonated beverages， and milk-containing beverages among primary school students were higher than those among middle school students （P

ObjectiveTo understand the distribution characteristics of trigger factors of foodborne disease outbreaks caused by Staphylococcus aureus and its enterotoxin in China.MethodsThe data from the national foodborne disease outbreak monitoring system and literature from 2010 to 2020 were collected and sorted out， and the data of Staphylococcus aureus and its enterotoxin was analyzed.ResultsA total of 703 outbreaks from 2010 to 2020 were included （694 in the monitoring system and 9 in the literature）. Single latitude attribution analysis found that meat accounted for 28.3% （199/703） of the causal foods， improper storage accounted for 15.2% （107/703） during the whole process， and catering service places accounted for 85.2% （599/703） of the occouring places. The results of multi-dimensional analysis showed that the number of events in each season was the largest in Eastern China. In addition to meat， pastry food and rice flour food were the main cause in eastern and southern China， which were mostly caused by improper storage. Among the outbreaks that occurred in catering service places， meat and flour rice food were mainly caused by improper processing， while pastry food was mainly caused by improper storage.ConclusionThe incidence of foodborne diseases caused by Staphylococcus aureus and its enterotoxin is high in meat products. It is necessary to strengthen the supervision of catering service places， food processing， storage and other sectors to reduce the risk of morbidity.

This review aims for a comprehensive insight into the interfacial reactions and the effects of surface metallization in high temperature die-attach, which is critical in governing the reliability of resultant interconnects of power electronic modules. With the emerging high-temperature filler materials, the interfacial interactions and microstructural evolutions exhibit various distinctive features, which demands detailed examination in order to identify suitable surface finishes. The metallization is not always beneficial to improving the quality and reliability of the interconnects, and consideration should also be given to the cost-effectiveness and manufacturability. The intermetallic compounds (IMCs) formed during interfacial reactions are of prime concerns for an extended discussion, together with the formation of solid solution at interfaces which can also be an important topic to explore. In this work, five commonly-encountered high temperature solder fillers are examined, including high-Pb, Au-based, Bi-Ag, Zn-Al solders and nano Ag paste, the emphasises are put on the interactions with different metallized surfaces in die-attach. The effects of metallization on interfacial reactions and formation of interfaces are discussed. Finally, the recommendations of suitable metallization are outlined to enable cost-effective and reliable interconnects for the related applications.

Timely and accurate monitoring is a prerequisite to survey the types, quantities, quality, and distribution of various natural resources. Currently, satellite remote sensing is the major observation method, which has advantages in observation scale, fast speed, and low cost. However, with the increasingly precise management of natural resource, satellite remote sensing faces some shortcomings in observation timeliness, dynamism, and accuracy. To solve these problems, combining space-based, air-based, and ground-based observation technologies can offer an effective approach by taking the advantages of each technology. This study focuses on development and applications of an integrated space-air-ground observation network to avoid the insufficiencies of individual monitoring method in natural resource monitoring and supervision. In this paper, we combined satellite remote sensing, drone photography, video surveillance, and field survey to establish an integrated space-air-ground observation network, proposed a cooperative observation mechanism in observation task, scale, and time. Then monitoring indicators and supervision process was established via indicator library and workflow engine, realizing closed-loop management of “discovery, analysis, verification, disposal, and cancellation” for natural resource monitoring and supervision. Afterward, by connecting the observation network and following the closed-loop management process, a cross terminal software was designed and developed to achieve process automation of natural resource monitoring and supervision. Finally, the observation network and software was put into practice, and the results indicate that the integrated space-air-ground observation network can effectively improve the efficiency and accuracy of natural resource of monitoring and supervision.

ObjectiveTo investigate and analyze the epidemiological characteristics of a wild mushroom poisoning event in Qinhuangdao City, identify the species of poisonous mushroom, summarize the experience of investigation and treatment, and put forward prevention and control measures, and provide reference for the treatment and prevention of wild mushroom poisoning patients.MethodsThe poisoning events were analyzed by using the method of epidemiological investigation, morphological identification and mushroom toxin detection.ResultsFour villagers in Qinhuangdao city had nausea, abdominal pain, diarrhea, sweating and shivering after eating wild mushrooms. Patients were treated with vomiting, gastric lavage, atropine and other symptomatic treatment in the hospital, and the prognosis of the patients was good. After morphological identification and toxin detection, it was determined that food poisoning caused by mushroom of inocybe.ConclusionThis is the first reported poisoning event caused by mushroom of inocybe in Hebei Province. The reason of poisoning was misguided by the Internet and poor self-awareness of food safety. Therefore, publicity and education should be strengthened, enhancing the awareness to prevent the poisoning of wild mushroom.

Under the engineering background of a + 144-m mining platform on an open pit slope of Xinqiao Mining Corporation, the eigenvalue distribution function of joints was acquired based on the massive statistics of field joints. Next, an orthogonal random joint model was constructed using the Monte Carlo method based on the UDEC software platform. Subsequently, the representative elementary volume (REV) size and occurrence effects of the equivalent elasticity modulus of the orthogonal random jointed rock mass were explored through numerical experiments with lots of discrete elements. The results showed that the equivalent elasticity modulus of the orthogonal random jointed rock mass was of evident size effect, and the relationship between the mean equivalent elasticity modulus Eeq and the REV size of the rock mass followed the negative power function distribution. Before the model size reached the REV size, its Eeq was greatly discrete. Under different joint angles, both the standard deviation σf and coefficient of variation δ of the equivalent elasticity modulus of this model presented discrete distribution. As the model size reached the REV size, the mean equivalent elasticity modulus Eeq showed “two-high and one-low” morphological distribution. Eeq was small when the main joint angle was α∈[30°, 40°], but it was large when α = 0° or 90°. δ was taken as 10%, so the REV size of the corresponding Eeq was 10 m × 20 m. When the model size reaches the REV size, the occurrence effect of its equivalent elasticity modulus was no longer significant.

Abstract Objectives The drug‐resistant seizures are characterized by frequent and severe onset of seizures in childhood. There is only little literature had extensively explored the types of pathological brain damage in Chinese children cases. The present study aims to investigate the histopathologic findings and seizure outcomes of drug‐resistant seizures in cases of 0–14‐year‐old children. Materials and Methods About 232 children cases were retrospectively who underwent epilepsy surgery. The medical records, onset age, age of surgery, disease course, seizure type, pathological reports, and seizure outcomes of these patients were retrospectively analyzed. Results The most common categories were malformations of cortical development (focal cortical dysplasia (FCD) was the most common type (94.36%, 67/71), found in 30.60% of the patients, tumors in 18.11%, glial scar in 12.50%, and encephalitis in 11.63%). It was found that the effective seizure outcome of FCD cases with shorter duration of epilepsy (

Ideological and Political courses are compulsory lessons for Chinese students throughout their schooling, which also are taken for granted as Citizenship Education courses by the authority. What's the real state of the lesson? Here we show you one example of the lesson.