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Hydroponic leafy vegetables can be enveloped and then clamped into the center of the planting hole in the cultivated pipeline, in order to avoid the root residues for the accurate root cutting of stems. However, the centering envelope grabbing mechanism with the fixed orientation can vary greatly with the different initial inclination angle and the position of hydroponic leafy vegetables. In this study, a variable orientation grabbing mechanism was proposed to adjust the orientation relative to the center of the planting hole during grabbing. Taking Lvbao hydroponic Chinese kale as the research material, the related properties were measured to determine the structural parameters. The initial opening angle of 15°, the closing angle of 30°, the rotating angle of 45°, and two times rotating speed of the two fingers were determined for the gripper during envelope grasping. A comparison test was performed on the grasping performance and success rate of the fixed and variable orientation grabbing mechanism with different initial inclination angles and positions using multi-body dynamics simulation with ADMAS software and laboratory grabbing test. The simulation results showed that the clamping inclination angle increased significantly with the increase of the initial inclination angle. At the initial inclination angles of 50°, 65°, and 80°, the mean clamping inclination angles of 84.25°, 85.86° and 87.76° for the variable orientation centering and clamping state, were better than those of 82.17°, 83.73° and 86.41° for the fixed orientation approach. At the position of P1 -P8, the mean clamping inclination angles of 84.89°, 85.93°, 84.81°, 86.86°, 85.16°, 86.47°, 86.70°, and 86.78° for the variable orientation centering and clamping state, were better than those of 82.67°, 85.09°, 84.64°, 85.09°, 84.13°, 83.17°, 83.94°, and 83.53° for the fixed orientation. The grabbing test also show that the grasping inclination angle increased, as the initial inclination angle increased. In the inclination angles of 45°-60°, >60°-75°, and >75°-90°, the mean grasping inclination angles of the variable orientation grabbing at different positions were 85.78°, 87.91°, and 87.57°, respectively, which were better than those of 83.08°, 85.00° and 86.76° for the fixed orientation. At the position of P1 -P8, the mean grasping inclination angles of 87.18°, 87.10°, 84.83°, 88.13°, 87.63°, 86.90°, 87.92°, and 88.21° for the variable orientation grabbing, were better than those of 80.89°, 86.98°, 88.07°, 85.88°, 81.56°, 83.99°, 85.51°, and 86.68° for the fixed orientation. In the hydroponic Chinese kale with different initial inclination angles, the mean values of grabbing success rate were 91.67%, 95.83% and 100.00% for the variable orientation, which were better than those of 87.50%, 91.67% and 100.00% for the fixed orientation. Except for the P2 position, the mean values of grabbing success rate of variable orientation grabbing at different position were higher than those of the fixed orientation. It infers that the simulation was consistent with the test. The variable orientation grabbing was more applicable for the better performance of the centering envelope grabbing mechanism. High-speed photographic images presented that the main reason for the grabbing failure at P2 was that the double-layer finger was directly contacted and pushed with the extended leaves of the hydroponic Chinese kale during entering and positioning. Therefore, it can be expected to avoid the collision of the fingers and the extended leaves in future. The finding can provide a strong reference for the harvesting equipment of hydroponic leaf vegetables. [ABSTRACT FROM AUTHOR]

[Objective] The study aimed to elucidate the effects of two kinds of organic potassium salt cigarette auxiliaries on the pyrolysis performance of cigarette paper. [Method] By adding two kinds of organic acid potassium salt with different concentrations to cigarette paper, the effects on the pyrolysis performance of cigarette paper were studied by means of simultaneous thermal analysis, mainstream smoke detection and sensory quality evaluation. [Result] With the increase of the concentration of potassium carbonate and potassium citrate, the initial temperature of thermogravimetric loss gradually decreased, and the increase of weight loss rate and weight loss in the initial heating period corresponded basically with the addition concentration. With the addition of potassium citrate in the cigarette paper, the number of smoking pons decreased gradually, and the content of nicotine and tar also decreased gradually. When the addition amount was 3 %, the release of CO was the lowest, and then increased with the increase of the addition amount. With the addition of potassium carbonate in cigarette paper increasing, the number of smoking mouthfuls firstly decreased and then increased slowly, and the content of nicotine and tar also showed a decreasing trend. When the addition amount of potassium carbonate in cigarette paper was 3.5 %, the content of nicotine in cigarette paper and the number of smoking mouthfuls were the least. When the concentration was 2.5 %, the CO content was the lowest. [Conclusion] The use of cigarette paper additives catalyzed the thermal cracking process of cigarette paper, which resulted in the decrease of tar and CO content in mainstream smoke and affected the sensory quality of cigarettes. [ABSTRACT FROM AUTHOR]

Head deviation ratio is a key technical indicator for length optimization in drip irrigation laterals. The deviation ratio in sub-surface drip irrigation is different from that in surface drip irrigation because the laterals are embedded and compressed in soil, and influenced by the submerged discharging. This study aimed to investigate head deviation property of subsurface drip irrigation laterals and its relationship with soil moisture uniformity. This experiment including 3 large pipe networks of subsurface drip irrigation in cotton field was carried out in Xinjiang. The drip irrigation pipe was buried in 28-33 cm below the soil surface. The length was 100 m. The spacing of pipes was 0.5 m in 2002, and 1 m after tye year of 2004. A total of 3 pairs of laterals were chosen out of upstream, medium-stream and downstream of the branch pipe. For each pipe network, more than 6 laterals were selected for the experiment. Among the laterals, some were ring network and some were tree network. The precision pressure gauge was used to measure the water pressure in the head and tail of laterals, and water meter to measure water volume at the beginning of laterals. During the experiment, the designed working pressure was 10 m. The soil moisture at depths of 30 cm along the laterals was determined by a soil moisture measuring instrument. The head deviation ratio and soil moisture uniformity was calculated based on soil moisture. The relationship between the laterals' head deviation ratio and soil moisture uniformity coefficient in 30 cm depths along the laterals was analyzed. The results showed that the head deviation ratio of the laterals were from 0.58% to 12.80%, meeting the requirement of Chinese microirrigation standard (smaller than or equal to 20%). Overall, the head deviation ratio in each lateral were different in a same pipe network with the value fluctuated in a certain range, whereas the changing trend was stable between tree-like laterals and ring-like laterals in a same branch pipe. The analysis on outliers of measured head deviation ratio showed that the deviation ratio may be affected by thickness of lateral wall. The lateral with thick wall had more stable hydraulic performance than that of the thin wall. During the entrance pressure of 7.32-11.75 m, the entrance pressure had no significant influence on head deviation ratio (P>0.05). The head deviation ratio was extremely negatively correlated with soil moisture uniformity coefficient (P<0.001). According to theoretical analysis, a model was established with soil moisture uniformity coefficient as response variable and head deviation ratio as independent variable. By comparing the calculated values and model-established values of soil moisture uniformity coefficient, we found the model was reliable in predicting oil moisture uniformity coefficient with the absolute error from -6.0% to 5.3% and 85% of laterals had the absolute error smaller than 5%. This study can provide valuable information for the length optimization of laterals, evaluation of working conditions, and management of operation in subsurface drip irrigation system. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the temporal and spatial migration of sediment in the sand filter column. Three kinds of sand filter columns (0.90-1.25, >1.25-1.60, and>1.60-2.0mm) were selected as the research object, and the sand filter layer was used as the fractal resistance model. The maximum pore diameters of the sand filter layers were 0.99, 1.14, and 1.41, and the average pore diameters were 0.41, 0.68, and 0.83. The Yellow River sediment of the People's Victory Canal was used as the raw water sediment impurity particles, where 0.4‰ muddy water was configured. The filtration rate was 2m³/h. After that, the filter column was removed to separate from the sediment during filtration. The quality of the sediment was calculated by the trapped filter layer of the three sand filter columns at different depths. The particle size distribution of sediment and sediment trapped by the filter column was measured by laser diffraction instrument. The results showed that the ratio of sediment intercepted by three filter columns was 97.08%, 94.53%, and 90.5%, respectively. The sediment intercepted by the surface filter layer accounted for 97.88%, 96.36%, and 81.48% of the total sediment intercepted by the filter column. Therefore, the smaller the particle size range of the filter column was, the larger the sediment retention ratio was, and the better the filtration effect was, but the more serious the surface filtration phenomenon was. An analysis was also made on the particle size distribution of the three filter layers at different depths. The D3 of the 0.90-1.25 sand filter column from the upper layer to the lower layer was 4.47, 1.00, 0.90, and 0.91μm. D98 was 476.30, 111.40, 98.31, and 97.79 μm. Span was 1.82, 5.13, 5.47, and 5.56; From the upper layer to the lower layer, D3 of ＞1.25-1.60 sand filter column was 3.77, 1.54, 0.97, and 0.99μm. D98 was 460.20, 344.20, 107.60, and 298.20μm. The Span was 1.95, 3.13, 4.50, and 4.47, and the D3 of ＞1.60-2.0 mm sand filter column from the upper layer to lower layer was 4.33, 3.50, 2.43, and 1.45 μm. D98 was 463.90, 456.00, 415.40, and 215.20 μm. The Span was 1.82, 1.86, 2.38, and 2.59. Consequently, the larger the filter column toward the lower layer was, the smaller the sediment particle size was, where the particle size tended to be concentrated. Each filter column was in the same depth of the filter layer, the larger the filter particle size was, the larger the particle size was, and the larger the particle size span was. Finally, the loss of sediment mass and particle size distribution were calculated using the sediment mass and particle size distribution intercepted by the sand filter column. Specifically, about 50% of the clay and silt particles of the original soil flew away in the process of the three sand filter columns, whereas, only 3% of the fine, medium and coarse sand of the original soil was lost. According to the hydraulic test, the smaller the particle size of the sand filter material composing the filter column was, the larger the reduction of the filter speed was, the larger the particle size of the filter material was, the gentler the flow rate was, the lighter the degree of blockage inside the filter column was, and the more stable the flow field of the water flow in the filter layer was. The larger the particle size of the sand filter layer was, the larger the pore diameter was, the slower the pressure rise was, and the stronger the anti-clogging ability of the filter layer was. This finding can provide a strong reference to optimize the layer thickness and particle size of the sand filter. [ABSTRACT FROM AUTHOR]

In order to seek phase change materials suitable for the construction field, this study proposes a decanoic acid (DA)- Cetyl alcohol (HD) eutectic phase change material, and the preparation of stereotyped composite phase change materials with different adsorption rates using hydrophobic fumed silica as porous adsorption material The thermophysical properties of the shaped composite phase change material with the maximum DA-HD adsorption rate were investigated. The hydrophobic fumed silica is used as the adsorption material, and the porous material is used. The shaped composite phase change material was prepared by adsorption method, and the DA-HD/fumed silica shaped composite phase change material was analyzed by DSC, FT-IR, SEM and TGA. The structure and properties were characterized. The results show that the optimal mass ratio of DA to HD in the DA-HD eutectic phase change material is 71.81∶28.19. The phase transition temperature is 23.64 ℃, and the latent heat of phase transition is 174.5J/g. The DA-HD eutectic phase change material was adsorbed into the nanopores of fumed silica, forming a It can form a stable three-dimensional structure, the maximum adsorption rate is 60%, and the adsorption process is only physical bonding without chemical reaction. Prepared DA-HD/fumed silica The phase transition temperature of the shaped composite phase change material is 19.20 ℃, the latent heat of phase transition is 93.1 J/g, and the phase transition temperature is within the comfortable temperature range for indoor environment, and Larger latent heat of phase transition and good thermal stability. [ABSTRACT FROM AUTHOR]

Backwashing of quartz sand filter in micro-irrigation is an effective way to realize the regeneration of quartz sand filter media. Analysis of flow field in the backwashing process of quartz sand filter and determination of reasonable backwashing velocity play an important role in the design and operation of the quartz sand filter. The method of numerical simulation has obvious advantage in the analysis and investigation of the flow field in the filter layer. In order to realize the numerical simulation of the backwashing process of quartz sand filter, the geometric model of quartz sand filter was established through Gambit software, and the mesh division of the geometric model was carried out. Because the backwashing process of quartz sand filter layer is a solid-liquid multiphase flow system interacted by both water and quartz sand, in which quartz sand particles are distributed only in a part of the region during the process of backwashing, not being carried away to outside of the filter by the stream, and in which quartz sand accounted for a larger proportion of the whole volume, the Eulerian model was adopted as a model for numerical simulation of backwashing. At the same time, because the backwashing process of quartz sand filter layer is a dynamically stable process, the transient simulation solver was adopted. The simulation objects were three kinds of quartz sand filter layer with the same thickness of 400 mm, but the equivalent particle size were 1.06, 1.2 and 1.5 mm respectively. In order to verify the reliability of simulation results, backwashing experiments were conducted in Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences, in 2014. The parameters such as backwashing velocity, pressure drop and expansion height of filter layer were measured. The simulation results were compared with the experimental results. Comparison showed that the maximum simulation error of the whole pressure drop of filter layer was 7.03%, and the maximum simulation error of filter layer density was 1.93%. It was proved that the numerical simulation results were reliable. On this basis, the fluctuation trend of pressure drop with time and the variation trend of the mean value and the standard deviation of the pressure drop with backwashing velocity in backwashing process of quartz sand filter layer were analyzed. If the standard deviation of pressure drop is large, it shows that the fluctuation of pressure drop is unstable, and the unstable fluctuation of pressure drop will affect the effect of backwashing. This result can determine the reasonable range of the backwashing velocity. Then, the distribution rule of the filter layer density with time, the variation trend of the mean value and the standard deviation of the density with the change of the backwashing velocity were analyzed. When the density is close to the static density of the mixture composed of water and quartz sand, the effect of backwashing is poor. When the standard deviation of density is too large, partial concentration phenomenon will appear in the filter layer, which will cause negative influence on the effect of backwashing. Thus, the reasonable range of the backwashing velocity was determined. After combined the rules of pressure drop fluctuation and density distribution, the reasonable ranges of the backwashing velocity of three kinds of filter layer are obtained as 0.0149-0.0212, 0.0146-0.0218 and 0.0191-0.0261 m/s respectively. The research results provided a theoretical basis for the mechanism of quartz sand filter in the process of backwashing. It also provided a technical support for the operation of the sand filter. [ABSTRACT FROM AUTHOR]