Search

The geometric similarity between two sets of coordinates should be assumed for frame alignment. When aligning Global Navigation Satellite System (GNSS) positions with seasonal variations to the linear Terrestrial Reference Frame (TRF), non-negligible aliasing errors of transformation parameters can appear and bias the station positions. The recent release of the seasonally augmented International Terrestrial Reference Frame 2020 (ITRF2020) necessitates an investigation into the impacts of seasonal terms on the alignment of regional networks. Using four-year of GPS data for Crustal Movement Observation Network of China (CMONOC) stations, we realize five sets of regional reference frames (RFs) aligned to the linear ITRF2020 (REF-LIN), the seasonal ITRF2020 (REF-FRQ), the linear ITRF2020 augmented either with seasonal signals or with full signals from loading models (REF-FIT and REF-NTL), and the combination of seasonal displacements from ITRF2020 and sub-seasonal signals from loading model (REF-CMB). Our analysis revealed that the augmented ITRF2020 had significant impact on the global stations used for frame alignment. Aligning daily solutions to the augmented ITRF2020 instead of the linear ITRF2020 resulted in a noticeable root mean square (RMS) decrease for over 70% of global stations. The REF-CMB method was the most preferred for frame alignment of global networks, with the largest decreased RMS of 0.3 and 1.0 mm in horizontal and vertical components. This indicates that most true signals are preserved in the aligned daily solutions. For regional network, we found only marginal impacts on regional stations in terms of linear velocity, residuals of time series stacking between the augmented solutions and REF-LIN. However, the larger discrepancies are noticed between annual estimates and loading model for the vertical component of REF-CMB and REF-FRQ, compared to RER-LIN solutions. [ABSTRACT FROM AUTHOR]

Global Navigation Satellite System (GNSS) network analysis benefits from precise point positioning with undifferenced (UD) or double differenced (DD) integer ambiguity resolution (IAR). Position time series with UD-IAR and a practical DD-IAR are compared for a mixture network consisting of 57 global and 82 regional stations with 4-year observations. The sparse global stations are more affected by different IAR methods than the regional stations of Crustal Movement Observation Network of China (CMONOC). The most significant differences between UD-IAR and the practical DD-IAR are observed in velocity estimations, with averages of 0.15 and 0.30 mm/yr for the horizontal and vertical components, respectively. UD-IAR can achieve smaller root mean square at 70–83 % of the daily solutions than the practical DD-IAR for global stations. Nevertheless, moderate differences of frame parameters and annual variations are introduced by different IAR methods. The IAR is also proved to be one of the potential origins for Global Positioning System (GPS) draconitic signals and white noise at high frequency. [ABSTRACT FROM AUTHOR]

Given the problem of the low tensile performance of the plastic film used in China, which brings about difficulties in curl-up film collecting, in this study, a contrast test was carried out on the tensile property of high-performance film for full recycling and the ordinary polyethylene film (PE film) that is used extensively in China. Test results showed that, within the service period, the elongation at break and tensile yield stress of the high-performance film were higher than those of ordinary polyethylene film, and, within the film-laying period of 0~30 days, the reduction scale of the elongation at break and tensile yield stress was higher than that within the film-laying period of 30~180 days. In this study, in order to obtain the lowest tensile performance of the film by curl-up film collecting, the operation principles of the curl-up film collectors were analyzed. The test on the force of curling up the film in the process of overcoming the force between the film and soil was analyzed. Test and analysis results showed that, for different sampling positions, film pick-up angles, and film types, the tensile stress on the film while pulling it up was within a range of 15.97~21.86 MPa. In order to verify the curling up effect of differently structured film collectors on different types of film with different thicknesses, a field test on film curl-up collecting was designed. A contrast test was carried out on two types of curl-up film collectors, 1JRM-2000 and 11SM-1.2, and the test results showed that the film recycling rate and working performance on the film laid in the same year by the film collector with a fixed film pick-up angle were higher than those for varying film pick-up angles. The curl-up film collector fixed with an automatic film-guiding mechanism is not affected by the velocity difference between the linear velocity of the film curl-up mechanism and the advancing velocity of the machine. The film recycling rate and working performance on the film laid in the same year by the 11SM-1.2 curl-up film collector can meet the operational requirements for collecting high-performance film with thicknesses of 0.008 mm and 0.01 mm. This research can provide a reference for simplifying the structure of residual plastic film collectors, increasing the film recycling rate, and reducing the cost. [ABSTRACT FROM AUTHOR]

The potato-soil separation device comprising five function areas (i.e., shearing, bending, throwing, cleaning, and conveying) was developed to address the mentioned problems (e.g., soil with high moisture content, large viscosity, and poor separation efficacy) in the harvesting process for winter idle paddy fields of Southern China. Given the kinetic analyses for the potato-soil mixture of five function areas, the crucial factors of the effect of potato-soil separation were determined. Subsequently, the orthogonal test of 4 factors and 3 levels was performed, and the percentage of small soil λ, the percentage of soil adhering to potato tuber γ, and damage rate of potato tuber K were adopted as assessment indexes. Regression analyses and programming for the orthogonal test result were conducted to optimize the device run parameters, and the optimal run parameters included the rotational speed of the soil-crushing mechanism of 84.18 r/min, linear velocity of second-stage lifting chain of 0.75 m/s, and inclination angle of lifting chain of 15.87°. The field experiments were performed with the modified potato harvester. As indicated from the result, the visible potato rate was 94.31% and damage rate of potato was 0.89%, and the requirement of the national standard was satisfied. This study presented technical feasibility data and equipment for potato-soil separation under sticky soils condition. [ABSTRACT FROM AUTHOR]

Cold-proof mode has widely been updated for some vineyards in Xinjiang Region of northern China. The cold-proof cloth is normally used to assist in soil buried operation for better insulation of heat and moisture in complete soil clearing. However, the machine is still lacking for the soil clearing of winter grape and cold-proof cloth recycling, particularly in the early stage of popularization and application for the cold-proof cloth assisted soil-buried mode. It is also difficult to realize the smooth winding of cold-proof cloth. In this study, a new speed control system was proposed for smooth winding of grape cold-proof cloth in spring in Xinjiang Region, China. The linear velocity of the cloth roll was set to be equal to the forward speed of the machine. This system automatically detected the winding state of the cold-proof cloth. In smooth winding of the cold-proof cloth, the theoretical rotation rate of the DC motor was calculated in real time, according to the real-time changes of forward speed in a machine and the radius of cloth roller. A PID controller was adopted to control the duty ratio of Pulse Width Modulation (PWM) signal, then to adjust the rotation rate of the DC motor, further to drive the cloth roller for winding the cold-proof cloth. As such, the forward speed of the machine was used to realize the real-time adjustment of rotation rate for the cloth roller. At the time of cold-proof cloth deflected winding, the rotation rate of the cloth roller was adjusted to advance or lag the target rotation rate so that the cold-proof cloth was to restore the smooth winding state. Specifically, this study included the structure design of grape cold-proof cloth winding device, the hardware and software design of the control system. A control model was established in Simulink module using the motor transfer function model. In the simulation, the PID parameters were set, where the gain coefficients of proportion, integral, and differential were 0.3, 0.2, and 0.000 05, respectively. A physical prototype was also processed for the speed system. The static calibration test was carried out for the rotation rate of the DC motor, in order to obtain the relation between the motor rotation rate and duty ratio of the PWM signal. A performance test was conducted to verify the feasibility of automatic deflection adjustment for the cold-proof cloth. The optimized mounting distance of 20 mm was achieved for the laser switching sensor. PID parameters in the simulation test were taken as the intermediate levels in the performance experiment for the rotation rate of the DC motor, where each coefficient was tested at 4 levels in turn. The optimized proportion, integral, and differential gain coefficient were 0.3, 0.1, and 0.000 05, respectively, indicating basic consistency with the simulated values. The steady-state response time of the control system was about 0.4 s with a response delay of about 0.1 s, indicating a relatively small influence and good control effect. The performance test of slant winding cold-proof cloth was carried out, where the flatness was taken as the evaluation index. It was found that the flatness of the cold-proof cloth was more than 90% and the average was 92.78%, suitable for the operational requirements. The speed system with better control performance can provide a technical reference for the design and optimization of recycling machinery for the grape cold-proof cloth. [ABSTRACT FROM AUTHOR]

A combined windrower has widely been used for oilseed rape harvest in recent years. However, there is a limit laying space in the small windrower with a narrow swath. The side transmission is also difficult as a result of the tangled and lodged rape, particularly in the branch involvement overhead during cutting and conveying. In this study, a feasible mechanism of inclined transportation was proposed for the large-branch involvement in the oilseed rape, thereby a novel device of inclined transportation was designed for a rape windrower. An inclined windrower table was used for the large laying space of the rape stalk, thereby improving the transport capacity along the transverse direction. A systematic analysis was made on the process of cutting, transporting, and laying stalk in the inclined transportation of a rape windrower, according to the geometrical and kinematic conditions of the stem in the smooth migration. As such, the structural and performance parameters were determined, including the reel speed, conveyor belt speed, and conveyor angle. A field test was conducted to evaluate the laying quality of inclined transportation in a rape windrower. An optimization was made on the structural parameters of working parts to establish the constraint equations of operating parameters for the inclined transportation windrower. A quadratic regression orthogonal experiment was carried out to explore the interaction factors on the laying quality. The evaluation indices included the laying angle, the laying angle difference between the upper and lower floor, as well as the variation coefficient of laying width and height. The ranges of experimental factors were obtained, where the rotate speed of the reel was 26-38 r/min, the linear velocity of the conveyor was 1.4-1.8 m/s, and the conveyor angle was 10-30°. Quadratic multivariate fitting regression and variance analysis were applied to clarify the influence of interaction factors on the performance of inclined transportation windrower. Results showed that the conveyor angle had the most significant influence on the laying quality. A multi-objective optimization model was established after the quadratic regression orthogonal experiment, according to the standard requirements of the rape windrower. An optimum combination of parameters was achieved, including the reel speed of 35 r/min, conveyor belt speed of 1.5 m/s, and conveyor angle of 27°. In the field test, the results showed that the average spread angle was 28.3°, and the relative error with the predicted value was 5.6%, under the optimal combination of parameters. The laying angle difference between the upper and lower laying floor was 5.4°, where the relative error with the predicted value was 12.5%. The variation coefficient of laying width was 9.6% with a relative error of 15.6%, while, the variation coefficient of laying height was 8.6% with a relative error of 11.7%. The accuracy of laying quality in the prediction model was verified by the field test. The swathing loss rate and operating efficiency were0.73% and 1.11 hm2 /h, respectively. The water contents of rape stem and grain were 47.9% and 9.7% after 4-day drying, which decreased by 35.1% and 74.4%, respectively, compared with those before, indicating a great benefit for the following picking and threshing. Compatibility tests of inclined transportation windrower were carried out in the winter rape areas, including the upper middle and lower reaches of the Yangtze River, as well as the spring rape area of North China. The results demonstrated that the inclined transportation windrower can realize smooth transportation, neat laying, high quality, and low loss swathing, suitable for the multi-cropping rape in two-stage harvesting. This finding can provide a sound reference to design and optimize the rape windrower. A further dynamic characteristic of rape stalk during transport and laying is necessary for the better performance of inclined transportation in the future [ABSTRACT FROM AUTHOR]

Different varieties of gift boxes are commonly used to pack eggs, in order to satisfy the demands of consumers. It has brought great difficulties for the automatic packing of eggs. At present, manual packing is often used in egg processing industry in China, considering the variable size of color box, the different quantity of each box, and the fragile physical characteristics of eggs. In this study, a flexible cartoning, and handling mechanism was developed for the color boxes to realize the automatic packing of eggs. The movement trajectory in a Cartesian coordinate manipulator was planned, using the trajectory planning algorithm, thereby to industrialize the flexible packing production line for an egg color box. Besides, the basic physical properties and the packing protection performance of the color box were tested, including drop test, pressure test, frequency sweep test and random vibration test, in order to ensure the stability and reliability for the manipulator holding the color box and avoid the damage of the eggs in the box that caused by the resonance of the production line. The protective performance parameters for the color box were detected, including the critical drop height, the non-damaged clamping force, the resonance frequency, and the non-damaged egg transport system excitation. In the drop test of color box, the results showed that the critical drop height of eggs in the box was 290 mm, while, in the pressure test, the eggs in the box cannot damaged when the clamping force of the color box was less than 870 N. In addition, the frequency test of the color box proved that the resonance frequency of the color box package was 10-15 Hz, and the random vibration test determined that the excitation of the system can meet Grms≤0.52 g²/Hz. The splint and the guide frame can be quickly disassembled under the constraints of the physical parameters for the color box. The egg box can be boxed with flexibility, high efficiency, and low damage using the central controller (Siemens PLC S7-200 Smart) and the touch screen (MCGS) according to the size, specification and quantity of the color box. The maximum effective strokes of the X and Z axial were 750 and 380 mm in the Cartesian coordinate manipulator in the production line. The X-axial velocity of robotic arm was adjustable from 0 to 199 mm/s, while the Z-axial velocity was from 0 to 149 mm/s. The maximum stroke of the Y-axial gripper plate movement was 200 mm, and the maximum linear velocity was 50 mm/s. The rated power of the machine was 1.5 kW. So far, the production line has been running for 11 months on the packaging line, where the mechanical equipment, software and hardware of control system were stable and reliable. An on-site test was performed on the production line for 10 days, showing that the packing efficiency with 6 boxes and 4 boxes in a color box were 96.2 and 120.4 boxes/h, respectively. Compared with manual packing, the efficiency can be enhanced by 4-6 times, indicating that 3-6 assistant workers can be saved, while the damage rate of egg was reach zero in the whole test process. The findings can provide a sound reference to the design and application of the automatic production line of color box for egg packing in food industry. [ABSTRACT FROM AUTHOR]

In the rice area of the Northeast China, the large amount of rice straw with low moisture content is tough to chop. However, the existing method of chopping combined auxiliary slitting could not meet the requirements of chopping under such condition, which could cause some problems such as incomplete straw crushing and unqualified rate of straw crushing. It would affect the subsequent land preparation and transplanting operations and caused problems such as machine blocking, straw floating before transplanting and seedling floating during transplanting. In order to solve these problems, this paper designed a straw chopper based on the principle of differential sawing, which could realize the same direction with different speed between the saw disc blade and the crushing knife to achieve supporting sawing. The friction force and relative linear velocity of crushing straw were increased to improve the crushing effect. Structural parameters of saw disc blade, crushing knife and other key components were designed through theoretical analysis, and the structure and operating parameters of the machine were preliminarily obtained. In order to improve the wind velocity and straw feeding performance of the crushing chamber, three kinds of fan blade forms, namely facade fan blade, reverse fan blade and diverse fan blade, were designed to compare with no fan blade through simulation analysis. Simulation results by Fluent showed that the facade fan blade could improve the wind velocity in the crushing chamber and contributed to improving straw fluidity, and the verification test was in accordance with the simulation results. According to the movement track of crushing knife and saw disc blade, the rotation speeds of them were designed. The rotation speed of crushing knife ranged from 1815 to 2475 r/min, accordingly, and the saw disc blade rotation speed ranged from 605 to 825 r/min, to be specific, the ratio of rotation speed between saw disc blade and crushing knife was 1/3 constantly. The dynamics analysis of straw crushing process showed that rotation speed of crushing knife and the tilt angle between the saw disc blade could affect crushing performance. Therefore, a field experiment of two factors with three levels was designed by using the average length of straw crushing and the crushing qualification rate as an evaluation index. The test results showed that the crushing knife rotation speed and angle of slope had a significant impact on average length of straw crushing and straw crushing qualification rate. Considering straw crushing performance and energy consumption, the optimal combination was determined as follows: The crushing knife rotation speed was 1800 r/min and the angle of slope was 65°, the corresponding saw disc blade rotation speed was 600 r/min. The field test results under the optimized combination conditions were as follows: the average length of straw crushing was 9.58 cm, the proportion of straw under 10 cm was 93.23%, and the scatter unevenness was 20.89%, which met the quality requirements of straw crushing and scattering in the northeast rice region. In the paper, a comparison test between the differential sawing rice straw chopper and the ordinary straw chopper was carried out. The filed test showed that the average length of straw crushing of the ordinary straw chopper was 13.42 cm, and the proportion of straw under 10 cm was 71.5%, which was not as good as the differential sawing rice straw chopper, and there was no obvious difference in the scatter unevenness between them. After the chopping operation, the same plow was used for the plowing operation, and the straw burying rate was 98.92% of the differential sawing rice straw chopper while the ordinary straw chopper was 90.21 %. Its successful implementation could greatly improve the operation effect for chopping rice straw and stubble on one hand, and on the other hand provided better growing surface conditions for rice. The design of the machine provided a basis for the popularization and application of straw mulching technology in northeast China. [ABSTRACT FROM AUTHOR]

Highways built on soft clay subgrade are more prone to subsidence due to the geotechnical characteristics of soft clay. Monitoring ground movements in this area is significant for understanding the deformation dynamics and reducing maintenance cost as well. In this paper, small baseline subset synthetic aperture radar interferometry (SBAS-InSAR) technique is exploited to obtain and investigate the time series ground surface deformation after the construction of a road embankment over soft clay settlement. Considering the important effect of temporal deformation models on the final accuracy of estimated deformation, both the linear velocity model and seasonal deformation model are utilized to conduct the comparative investigation of deformation time series. Two highways in Fuoshan, China—G1501 Guangzhou Belt Highway and Lungui Highway—were selected as the test area. Thirteen TerraSAR-X images acquired from October 2014 to November 2015 were analyzed. Comparative study based on two groups of analyses generated from the two models for both highways were conducted. Consequently, several feature points distributed near the two highways were analyzed in detail to understand the temporal evolution of the settlement. In order to evaluate the reliability of our measurements, the residual phase was analyzed to assess the modelling accuracy of the two models. In addition, leveling data were also used to validate the experimental results. Our measurements suggest that the seasonal model is more suitable for the test highways, with an accuracy of ±3 mm with respect to the leveling results. [ABSTRACT FROM AUTHOR]

Exposure to phthalates has been found to have adverse effects on male reproductive function in animals. However, the findings from human studies are inconsistent. Here we examined the associations of phthalate exposure with semen quality and reproductive hormones in a Chinese population using phthalate metabolite concentrations measured in semen as biomarkers. Semen ( n = 687) and blood samples ( n = 342) were collected from the male partners of sub-fertile couples who presented to the Reproductive Center of Tongji Hospital in Wuhan, China. Semen quality parameters and serum reproductive hormone levels were determined. Semen concentrations of 8 phthalate metabolites were assessed using high-performance liquid chromatography and tandem mass spectrometry. Associations of the semen phthalate metabolites with semen quality parameters and serum reproductive hormones were assessed using confounder-adjusted linear and logistic regression models. Semen phthalate metabolites were significantly associated with decreases in semen volume [mono-n-butyl phthalate (MBP), mono-(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP)], sperm curvilinear velocity [monobenzyl phthalate (MBzP), MEHP, the percentage of di-(2-ethylhexyl)-phthalate metabolites excreted as MEHP (%MEHP)], and straight-line velocity (MBzP, MEHP, %MEHP), and also associated with an increased percentage of abnormal heads and tails (MBzP) (all p for trend <0.05). These associations remained suggestive or significant after adjustment for multiple testing. There were no significant associations between semen phthalate metabolites and serum reproductive hormones. Our findings suggest that environmental exposure to phthalates may impair human semen quality. [ABSTRACT FROM AUTHOR]

Building deformation models consistent with reality is a crucial step for time-series deformation monitoring. Most deformation models are empirical mathematical models, lacking consideration of the physical mechanisms of observed objects. In this study, we propose an improved time-series deformation model considering rheological parameters (viscosity and elasticity) based on the Kelvin model. The functional relationships between the rheological parameters and deformation along the Synthetic Aperture Radar (SAR) line of sight are constructed, and a method for rheological parameter estimation is provided. To assess the feasibility and accuracy of the presented model, both simulated and real deformation data over a stretch of the Lungui highway (built on soft clay subgrade in Guangdong province, China) are investigated with TerraSAR-X satellite imagery. With the proposed deformation model, the unknown rheological parameters over all the high coherence points are obtained and the deformation time-series are generated. The high-pass (HP) deformation component and external leveling ground measurements are utilized to assess the modeling accuracy. The results show that the root mean square of the residual deformation is ±1.6 mm, whereas that of the ground leveling measurements is ±5.0 mm, indicating an improvement in the proposed model by 53%, and 34% compared to the pure linear velocity model. The results indicate the reliability of the presented model for the application of deformation monitoring of soft clay highways. The estimated rheological parameters can be provided as a reference index for the interpretation of long-term highway deformation and the stability control of subgrade construction engineering. [ABSTRACT FROM AUTHOR]

The graphical method is one of classic location approaches. The location method locates an event using its hypocentral loci, and therefore has outstanding advantages such as visuality and robustness. However, its location accuracy is not high because it is usually based on homogeneous or laterally homogeneous models far from the real Earth. When the velocity structure is complex, hypocentral locus equations can hardly be solved analytically. In order to overcome the disadvantage of the graphical location approach, a numerical scheme is presented for solving hypocentral locus equations by linear interpolation. The equation of a hypocentral locus is solved in the residual (between observed and calculated arrival time difference or arrival time) field. As for each model node, it is combined with its adjacent nodes differing from it in residual polarity (positive, zero, or negative) into node pairs. Among these node pairs, the one with maximum absolute gradient is referred to as a normal node pair. Assuming that the residual varies linearly from positive to negative between the two ends of a normal node pair, the zero point of the residual between the two end nodes is determined as a solution to the hypocentral locus equation by linear interpolation. Numerical examples show that the presented method is adapted to complex velocity models and has no restrictions in the stability and the number of hypocentral locus segments. Compared with other approximate solutions, such as nodes with small absolute residuals or nodes of the elements traversed by the hypocentral locus, the ones determined by the interpolation method have much higher accuracy. This work is supported by the Natural Science Foundation of China (41374098 and 40974050). [ABSTRACT FROM AUTHOR]