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The air distribution and speed uniformity of the cleaning fan in the cleaning room have a great influence on the working quality of the cleaning system of the harvester. In view of the problem of uneven air distribution in the cleaning room caused by improper adjustment of the main operating parameters of the cleaning fan in the cleaning device of the corn combine harvester, this paper takes the self-developed air screen cleaning test bench as the object. The main working parameters of the cleaning centrifugal fan (air supply distance, fan speed, and number of blades) were simulated and the Fluent simulation software was used to carry out the single-factor and multi-factor optimization tests, explore the influence law of each test factor on the air velocity in front of the screen, in the middle and behind the screen and the deviation degree of the airflow at the back of the screen surface, and find the optimal parameter combination. The data were systematically analyzed by multiple regression method and variance analysis method. The regression model of air velocity at the front, middle, and back of the screen and the air deviation degree at the back of the screen surface for the three working parameters of the cleaning fan were established. The optimal working parameter combination was obtained, that is, when the air supply distance is 580 mm, the fan speed is 1000 r/min, and the number of blades is 10, the airflow velocity in front of the screen is 10.8 m/s, the airflow velocity in the middle of the screen surface is 11.8 m/s, the airflow velocity at the back of the screen surface is 11.2 m/s, and the airflow deviation degree at the back of the screen surface is 13.5%. The relative errors were 1.9%, 0, 2.8%, and 3.0%, respectively. A combined test of the fan and the cleaning screen body with a feeding capacity of 8 kg/s was carried out, and the loss rate was 1.15% and the impurities rate was 1.24%. The regression model was reliable, and the optimal operation parameter combination performed well, meeting the technical requirements of cleaning operation, and providing theoretical guidance for the adjustment of fan structure and operation parameters in the cleaning system of the grain harvester.

Automated guided vehicle technology has become a hot area of scientific research due to its increasing use in manufacturing and logistics. Its main features are programming and control, remote computer eye tracking, command receiving and execution, autonomous route planning, and autonomous driving execution of tasks, with the advantages of high intelligence and flexibility. In this work, a simple vehicle model is used to study the route planning and tracking control of automatic guided vehicles. This paper uses wireless communication to find the optimal route planning problem. Using geometric methods, we develop a model of the working environment of the mobile automatic guided vehicle and develop a route finding algorithm. Based on the kinematic model, an advanced routing controller is designed to conduct experimental simulation of two trajectories and verify the effectiveness of the trajectory tracking controller. When the time is after 2 s, the position error is almost completely zero. In the path planning, when the number of iterations is greater than 10, the path length remains constant, verifying the effectiveness of the method in this paper.

In order to address the problems of low energy storage capacity and short battery life in electric vehicles, in this paper, a new electromechanical-hydraulic power coupling drive system is proposed, and an electromechanical-hydraulic power coupling electric vehicle is proposed based on this system. The system realizes the mutual conversion between mechanical energy, hydraulic energy, and electric energy through the electromechanical–hydraulic coupler. This paper describes the structural characteristics and working principles of the system and analyzes the different working modes during the driving of the vehicle. We established a mathematical model of the hydraulic accumulator and the hydraulic pump and motor. Based on the vehicle dynamics model, an AME Sim vehicle model was built and the vehicle, and the relevant hydraulic parameters were set in combination with the actual situation. The braking energy recovery and release process was jointly simulated by AME Sim and Simulink. The simulation results show that the hydraulic accumulator size of the accumulator volume can influence the maximum working pressure of the accumulator and the SOC of the vehicle battery, and it is verified that 35 L is the best capacity. This study has an important reference value for matching electromechanical–hydraulic coupling parameters of electric vehicles.

Microstructure and texture evolution of a low-Ni Cr–Mn–N austenitic stainless steel were analysed during three-point bending process. The electron back-scattering diffraction (EBSD) was used to characterise the microstructural evolution with respect to two regions encompassing (I) near the inner corner and (II) near the outer corner. The fraction of deformation-induced martensite of either types (e- and α′-martensite) was analysed in both regions. The region (I) possessed a considerably higher fraction of e-martensite than that in the region (II). In the region (II), the fraction of austenite 60°/〈111〉 twins was increased. Moreover, in the region (I), the $$\left\{10\bar{1}2\right\}\langle \bar{1}011\rangle$$ extension twinning was depicted in e-martensite. The mean kernel average misorientation of e-martensite experienced a trivial change with increasing bending angle after reaching to a saturation point. Upon bending, texture measurements of austenite returned the αγ-fibre orientations with the dominant Brass component. However, a decrease in the Cube and S texture components was identified. The e-martensite texture revealed strong intensities along the $${\left\{hkil\right\}}_{\upvarepsilon }$$ -fibre. Besides, the α′-martensite developed $$\left(001\right){\left[0\bar{1}0\right]}_{{\alpha^{\prime}}}$$ and $$\left(001\right){\left[001\right]}_{\mathrm{\alpha^{\prime}}}$$ orientations with a trace of $$\left(113\right){\left[4\bar{7}1\right]}_{{\alpha^{\prime}}}$$ orientation.

In this paper, according to the design technical requirements, the completion of the structural scheme design of compound-driven in-pipe robot, the establishment of the cam active support diameter reducing mechanism mathematical model, obtain the relationship curve between its parameters, and completed the optimization of the cam contour. The resident performance of the robot in the pipeline is analyzed, and the feasibility of the robot's active resident in the pipeline is verified. This paper explores the relationship between the running speed of the robot in the pipeline and the leakage clearance under the condition of the fluid driven, and through the analysis and calculation of the different fluid velocity in the pipe, the reasonable range of the leakage clearance of the robot can be determined, for this range the robot can run smoothly. It has important theoretical value and engineering practical significance for the design and practical application of compound-driven pipeline robot.

Background Studies investigating the associations of maternal syphilis treatment with birth outcomes mainly concentrated in economically developed areas. Limited data are available in economically underdeveloped areas, such as Jiangxi Province. The study aims to investigate the impact of maternal treatment on birth outcomes in Jiangxi Province, China. Methods Data were obtained from the China’s Information System of Prevention of Mother-to-Child Transmission in Jiangxi Province. All syphilis infected pregnant women who delivered ≥28 gestational weeks and were registered in this system between 1 January 2013 and 31 December 2019 were enrolled. Pregnancy outcomes were evaluated by group-specific analyses according to their treatment status, adequacy and initiation time. Results 4210 syphilis infected pregnant women were included in the analyses. Infants born to untreated mothers (n = 1364) were at significantly higher risk for stillbirth (adjusted odds ratio (aOR) = 1.74, 95% CI, 1.01–3.00, P = 0.045), preterm birth (aOR = 1.27, 95% CI, 1.02–1.59, P = 0.034) and low birth weight (LBW) (aOR = 1.44; 95% CI, 1.11–1.86, P = 0.006) than those born to treated mothers (n = 2846) after adjustment for confounding factors. A significantly higher risk of stillbirth (aOR = 3.68; 95% CI, 1.62–8.34, P = 0.002), preterm birth (aOR = 2.26; 95% CI, 1.71–3.00, P P P n = 1299) than those treated adequately (n = 1547). No pregnant women who initiated the treatment in the first trimester (n = 682) delivered a neonatal CS case. Compared with mothers who initiated treatment in the first trimester (n = 682), those initiated in the third trimester (n = 1234) suffered an increased risk of stillbirth (aOR = 4.48; 95% CI, 1.31–15.30, P = 0.017), preterm birth (aOR = 2.34; 95% CI, 1.61–3.40, P P Conclusions Maternal treatment, especially early and adequate treatment, plays a crucial role in mitigating adverse pregnancy outcomes among syphilis infected women.

Hydrogen storage and transportation are the intermediate link of hydrogen production and the point of end-use. Standards for hydrogen storage and transportation published by ISO, CGA, NFPA, ASME, ANSI, SAC, CEN and JISC are reviewed and analysed in this paper. Numbers of standards for hydrogen embrittlement are more than the others. Standards for hydrogen piping and pipelines are only published by CGA and ASME. Chinese GB standards are mainly focused on general design and safety, gaseous hydrogen receptacles and hydrogen embrittlement. Standards for liquid hydrogen storage receptacles and safety, hydrogen piping and pipelines, and hydrogen transportation should be emphasized.

Safety standards are foundation for the deployment and development of hydrogen industry. In this paper, standards for hydrogen safety published by ISO, IEC and SAC are summarized and discussed. Standard framework of hydrogen safety is analysed. ISO standards are mainly focused on general safety standards and safety standards of hydrogen production. IEC standards are mainly focused on safety standards of fuel cell and fuel cell applications. China has basically established a safety standard framework for hydrogen industry. Safety standards for different stage of hydrogen industry are discussed and analysed. Suggestions of safety standards preparation for China are proposed.

The accurate and timely estimation of winter-wheat yield at the field and regional scales is critical to developing agricultural management strategies and reducing the effect of changes in environmental conditions on crop yield. Growth status and trend (GST) monitoring has been widely applied to estimate agronomic parameters using remote sensing methods. Many studies have employed GST monitoring, however, most of them were based on a single agronomic parameter and can therefore only represent one-sided or local GST information. Additionally, each agronomic parameter is interactive. Meanwhile, little studies have systemically combined multiple agronomic parameters into one comprehensive indicator to estimate crop yield using remote sensing data. Thus, the objectives of the current research were to build a comprehensive yield evaluation indicator (CYEI) using the improved fuzzy comprehensive evaluation (FCE) method and evaluate the performance of CYEI to monitor GST and estimate yield. The results showed that the CYEI can fully reflect the information of the leaf area index, leaf biomass, leaf water content, and leaf nitrogen content. Compared with various agronomic parameters, the CYEI based on the improved FCE method was more closely correlated with the yield (the R2 values of the validation set were 0.63, 0.69, and 0.63 at the booting stage, anthesis stage, and milk development stage.). The CYEI was estimated using a linear model constructed using the optimal VIs, and the results for the three growth stages achieved a higher precision (R2 = 0.74, 0.74, and 0.68 for the booting, anthesis, and milk development stages, respectively) than the traditional single agronomic parameter. The CYEI and Bayesian information criterion were then used to select VIs and then build a partial least squares regression model to estimate the yield. The estimation accuracy was found to be satisfactory, with R2 values of 0.55, 0.64, and 0.66 at the booting, anthesis, and milk development stages, respectively. Finally, a more intuitive image-scale yield monitoring method was obtained based on unmanned aerial vehicle remote sensing hyperspectral imagery. In the future, the proposed method can be used to obtain wheat growth information and provide a new prediction indicator to better estimate yield in precision agriculture.

Vibration-based piezoelectric energy harvesting technique is a promising way for power supply of smart and mobile wireless sensor networks. The novel structures of harvester with low frequency, wide bandwidth and large output power have drawn great attention. In this paper, vibration energy harvester with unsymmetrical, interdigital pick-up structure and voltage synchronous management circuit have been designed, fabricated, and characterized. The working bandwidths of 11.2 Hz at simulation and 12.3 Hz at experiment have been gained for the designed structure based on mode separation technique in a low vibrational frequency range (below 25 Hz) with the acceleration of 1 g . Experimental results show that the proposed harvester can generate the output power of about 151.3 μW (5.91 times of our previous work), which can maintain the normal work of given electronic devices (containing 18 light emitting diodes) by using a matched voltage synchronous management circuit. These results make it a promising candidate for power supply of low power micro electron devices in some special low frequency vibration environment, such as large engineering, bridge monitoring, wildlife monitoring, etc.

The detailed evolution of microstructure and texture of a low-Ni Cr–Mn–N austenitic stainless steel under bending deformation was studied. The effect of austenite grain orientation on the deformation-induced transformation and deformation twinning mechanisms was investigated in selected grains of analogous orientation located near the outer and inner radius, where distinct deformation mechanisms have been identified in different regions accordingly. With moving towards the outer radius, the concurrent occurrence of transformation- and twinning-induced plasticity was detected, while with moving towards the inner radius, twinning-induced plasticity was hindered. Texture of austenite showed the characteristic single fibre for face-centred cubic materials with a stronger intensity around the αγ –fibre. The deformation-induced e-martensite returned an intense { h k i l } e fibre. The 10 1 ‾ 2 " open=" 1 ‾ 011 e extension twinning was detected only in regions near to inner radius. Interestingly, the deformation-induced αʹ-martensite showed the uncommon h 11 " open=" 1 / h , 1 , 2 fibre upon bending deformation.

The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Si O Si and Si O M chemical bonds. The optimum corrosion resistance of the coating in the corrosive media is obtained by 25 ml L −1 BTESPT modification. This whole study implies that the cerium conversion coating modified with certain silane agent deserves cautiousness before its application for corrosion resistance.

Under the background of the reform of macro-market economy system, the realistic value of technology to modern enterprise competition is more and more prominent, and its innovation drives the development and progress of the whole society. Colleges and Universities are the main force of scientific and technological innovation, gathering rich intellectual resources and playing an irreplaceable role in building an innovation-oriented country. However, the success rate of technology incubation in colleges and universities is relatively low and individual problems emerge one after another, resulting in a certain degree of waste of resources, which is the focus that must be addressed at present. This paper briefly analyzes the problems existing in the technology incubation of colleges and universities and probes into the corresponding countermeasures.

In this study, microstructure and mechanical properties of a friction stir welded 18Cr–2Mo ferritic stainless steel thick plate were investigated. The 5.4 mm thick plates with excellent properties were welded at a constant rotational speed and a changeable welding speed using a composite tool featuring a chosen volume fraction of cubic boron nitride (cBN) in a W–Re matrix. The high-quality welds were successfully produced with optimised welding parameters, and studied by means of optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and standard hardness and impact toughness testing. The results show that microstructure and mechanical properties of the joints are affected greatly, which is mainly related to the remarkably fine-grained microstructure of equiaxed ferrite that is observed in the friction stir welded joint. Meanwhile, the ratios of low-angle grain boundary in the stir zone regions significantly increase, and the texture turns strong. Compared with the base material, mechanical properties of the joint are maintained in a comparatively high level.

The relationships between microstructure, texture, grain boundary and tensile strength, Charpy impact toughness of (Nb+Ti+V) stabilised Fe–17Cr ferritic stainless steel thick plates were investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, tensile and Charpy impact testing. The results show that for Fe–17Cr ferritic stainless steel thick plate, the addition of warm rolling procedure leads to refinement of grain size, modification of texture, and then optimisation of grain boundary, including grain boundary character distribution and grain boundary connectivity. Meanwhile, the mechanical testing results indicate that optimal transformation that warm rolling procedure brings to Fe–17Cr ferritic steel thick plate is beneficial to its mechanical properties.

The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe 2 Nb (Laves phase) and Cr 23 C 6 formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe 2 Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe 2 Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe 2 Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe 2 Nb particles.

The microstructure, including grain size and precipitation, tensile strength and Charpy impact toughness of (Nb + V) 18Cr–2Mo ferritic stainless steel heavy plates with/without Ti were investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and standard tensile strength and Charpy impact toughness testing. It was found that for 18Cr–2Mo heavy plate, a good combination of Nb–V stabilized method without Ti induces refinement of grain sizes due to the precipitation of amounts of fine Nb carbonitrides and V nitrides. Meanwhile, the mechanical testing results indicate that optimal transformation of grain size, precipitation that Nb–V composition system brings to 18Cr–2Mo heavy plate is beneficial to improvement of strength and impact toughness.

Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.

Thin plates of 21% Cr ferritic stainless steel welded by pulsed gas tungsten arc welding at different pulse frequencies were investigated for the microstructure characteristics and hardness behavior. The welds contained columnar grains in the outer part and fine equiaxed grains in the central region due to the pulsed process.

A 2-position analytic alignment method for strapdown inertial navigation system (SINS) is developed to overcome the limit on precision in analytic alignment on stationary base, which mainly comes from the performance of inertial measurement unit (IMU). IMU is successively rest at two positions by rotating the vehicle to measure the earth's rotation rate and gravity, and measurement at one position is subtracted from the other to eliminate constant error of IMU to improve alignment precision. Transformation matrix between two vehicle reference frames is calculated using output of gyros during the vehicle's rotation. An improved method for estimating gesture matrix is developed to avoid matrix nonreversibility. Error analysis is performed to determine the available precision which is demonstrated by computer simulation.