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Goji (Lycium barbarum L.) is one of the most popular medicinal plants, particularly as a typical nutritional fruit supplement rich with bioactive compounds. However, fruits browning, taste loss, and storage intolerance often occur during postharvest, because of tender and juicy tissue. Among them, the temperature is one of the most significant factors to maintain the quality and extend the shelf life of fruits. It is necessary to place fruits in a constant temperature environment after harvest since temperature fluctuations and variation tend to induce product quality deterioration. This study aims to investigate the effect of precise temperature control on storage quality and aroma components of fresh goji fruits. Three treatments of storage temperature at 0℃ were also set, including foam box (CK), foam box + cool storage agent (ice temperature), as well as the precise temperature control box and cool storage agent (phase temperature). The temperature was real-time recorded in different cabinets to evaluate the storage quality. Principal component analysis (PCA) was used to evaluate the aroma components of goji. Results showed that the foam box containing the self-made refrigerant performed better at ambient temperature, compared with that with the ice. Temperatures in the box of CK, ice, and phase temperature group were (0.12±0.17), (-0.04±0.07) and (-0.05±0.04)℃, respectively, during the whole storage period. A cold accumulator provided a cold source in the box to maintain a low-temperature environment. The temperature distribution was more uniform in the precision temperature control box, while the maintenance time of low temperature was longer than before, due to the excellent performance of heat preservation. The time of mildew and rot in the CK group, ice, and phase temperature group were 10, 20, and 40 d, respectively. At the storage of 40 d, the rot rate, mildew rate, and soft fruit rate in the phase temperature group were 4.11%, 4.50%, and 5.08%, respectively, much lower than 14.85%, 15.44%, and 15.01% in the CK group. Chromatic aberration ΔE was lower than 3, while Brightness L value reached 34.12. The content of soluble solid, titratable acid, Vitamin C conten, carotenoid were 0.65 percentage, 0.03 percentage, 4.34 mg/100g, 2.90 mg/g higher than CK group, respectively. Correspondingly, the treatment in the phase temperature group inhibited the increase of decay rate and weight loss rate, indicating the delay of ΔE and L, as well as a higher soluble solid, titratable acid, VC, and carotenoid content. The principal component analysis demonstrated that the goji quality in three groups was in the order of phase temperature group, ice temperature group and CK group. Moreover, the contents of favorable aroma components, such as lycium aldehydes and terpenoids, were relatively higher in the storage under precise temperature control. Consequently, the ice and phase temperature storage was the most effective in the long-term preservation of goji, where the color change of goji was delayed to facilitate the release of volatile substances, while effectively prolonging the storage period of goji to 30 days. The finding can be greatly beneficial to guide the preservation of goji fruits. [ABSTRACT FROM AUTHOR]

Land use/land cover change (LUCC) is one of the important driving forces of ecosystem services change. Because ecosystem services depend on different ecological and geographical processes on different spatial and temporal scales, it is of great significance to study ecosystem services based on LUCC. In recent years, the LUCC in the Lower Yellow River has changed obviously, which has a huge impact on the regional ecological environment. Strengthening the research on the land use and Ecosystem Services Value (ESV) can effectively promote the protection of the ecological environment in the Lower Yellow River, which is of great significance for the sustainable development of the whole Yellow River basin ecosystem. Based on the land use classification data of the Lower Yellow River from 1990 to 2015, using the land use change degree and land use transfer matrix, this paper explored the spatiotemporal distribution of land transfer change, and used the equivalent factor method, hot spot analysis and focus model to explore the spatiotemporal evolution and spatial heterogeneity of the county ecosystem service value in the Lower Yellow River. The results showed that: 1) During 1990-2015, the area of farmland, grassland and unused land decreased by 2 894, 1 476 and 856 km² respectively, and the area of built-up land increased by 4598 km² . Farmland was the main contributor of the increase of built-up land. 2) From the perspective of spatiotemporal scale, the ESV of the Lower Yellow River decreased by1.885 billion yuan in 25 years, and the areas with higher average ESV decreased gradually, while the areas with lower average ESV increased gradually. The ESV at the county level changed obviously, and most of the regions showed a downward trend. Sensitivity analysis showed that the ESV of the Lower Yellow River was inelastic to the value coefficient. Even though the value coefficient was uncertain, the calculation of ecosystem services in the whole study area was still stable, which could prove that the research results were credible. 3) From 1990 to 2015, the spatial concentration degree of the high value and low value areas of average ESV in the Lower Yellow River was obvious, but there was a trend of gradual weakening. The barycenter of ESV was located in Yuncheng County, Shandong Province. The ecosystem service value of Shandong Province was always higher than Henan Province. 4)The spatial differentiation of ecosystem service value in the lower reaches of the Yellow River was influenced by the interaction of natural factors, social factors and economic factors, and was the result of the interaction of different driving factors, among which the human comprehensive impact index has the greatest impact on the spatial differentiation of ecosystem service. Therefore, the ecological protection of the Yellow River should strengthen the protection of the vulnerable areas of the ecosystem, strengthen the construction of regional ecological barriers, build the evaluation system of the coordinated development of the ecological economy, and realize the high-quality development of the ecological economy in the Lower Yellow River. [ABSTRACT FROM AUTHOR]

Timely and accurate information of crop planting structure is of great significance for monitoring agricultural conditions, estimating crop yield, adjusting agricultural structure and formulating food policies. However, currently only little explicit information about spatial crop patterns is known, especially in China where the farmland landscapes are extremely fragmented and heterogeneous. At present, techniques for quantifying crop spatial patterns may be insufficient to map crops in complex planting areas, the plot sizes of which are smaller than the spatial resolution of ready-to-use satellite data. In order to achieve the fine mapping of crops in complex planting areas, this study aimed to explore approaches that simultaneously mapping multiple crops on parcel scales with high spatial resolution images. A 2.9 km×2.6 km complex heterogeneous planting area in the suburb of Wuhan, Hubei Province was selected as the typical study area. Combined with high spatial resolution images, an improved method of fine crop mapping based on geo-parcels was presented. Using the spectral, shape and texture information of images, combined with random forest (RF), artificial neural network (ANN), and K-nearest neighbor (KNN) algorithms, WorldView-2 images were accurately classified through the following steps. First, Worldview-2 images were visually interpreted to obtain the distribution of cropland and non-cropland in this study area, so as to mask out non-cropland information in remote sensing images. Second, the pre-processed WorldView-2 images were segmented by using the land parcel boundary vector data obtained from manual visual interpretation, and 32 feature variables of the image object were extracted, including NDVI, area, GLCM-correlation, etc. Third, the ReliefF-Pearson feature dimension reduction method was adopted to remove redundant features with high correlation and weak classification ability. Then, RF classification was performed with optimal features and field sampling data, and the accuracy of the classification results was evaluated. Subsequently, the accuracy of RF classification was compared with that of ANN and KNN to verify the effectiveness of RF algorithm. Finally, four feature combination sets were constructed based on optimal features, and RF classification accuracy was compared under four feature combinations to evaluate the contribution of shape and texture features to crop classification. The results showed that 1) The 12 feature variables, such as RVI, NDVI, GLCM-correlation and border length, were the optimal features of parcel-level crop classification based on high spatial resolution images, which can fully characterize image features and reduce data redundancy; 2) The RF method had the highest classification accuracy, with an overall accuracy of 79.07%, kappa coefficient of 0.76, and the overall accuracy of KNN and ANN method was above 70%; 3) Compared with the method of only using spectral features, adding shape or texture information could effectively improve the accuracy of crop classification, and the overall accuracy could be improved by 3.86% and 3.05%, respectively; 4) Based on the optimal features and RF classification method, the classification accuracy of rice, cotton, lotus, bare upland field and bare paddy field was over 80%, while that of abandoned cropland, peanut and ‘other crops’ was only about 60%. This study provides new ideas, methods and technical means for realizing the fine classification of crops by remote sensing in complex planting areas, and can provide references for accurate survey of crop planting information, refined management of rural land use and dynamic monitoring of agricultural industrial structure adjustment. In the future, the image segmentation technology will be further studied to ensure the consistency between segmentation objects and geographical entities as much as possible, and improve the accuracy and automaticity of crop remote sensing classification on parcel scales. [ABSTRACT FROM AUTHOR]

Moisture content of the aquatic feed after extruder is frequently high in the production process, and drying is necessary to reduce moisture content of the aquatic feed. The thickness of feed layer is an important parameter during the aquatic feed drying. On one hand, the thickness of feed layer represents the capacity of the belt dryer per unit time(the thicker the feed layer, the higher the productivity), which affects the working energy consumption of the belt dryer. On the other hand, the thickness of feed layer also affects airflow distribution inside the belt dryer, thus affecting the distribution uniformity of airflow velocity on the surface of feed layer. The airflow velocity on feed layer surface directly influences the moisture content of aquatic feed after drying, and the uniformity of airflow velocity on feed layer surface directly influences the uniformity of moisture content of aquatic feed. In this paper, effects of aquatic feed layer thickness on airflow distribution in belt dryer and airflow velocity distribution on feed layer surface was studied. Firstly, three different kinds of internal airflow distribution inside the belt dryer were simulated using computational fluid dynamics (CFD), corresponding to three kinds of feed layer thicknesses (20, 30, 40 mm). Secondly, a belt dryer was designed and manufactured as the experimental platform based on the actual production needs in the National Feed Processing Equipment Engineering and Research Center. Thirdly, three series of experiments were conducted using the experimental platform corresponding to three kinds of feed layer thickness (20, 30, 40 mm). And repeat three times in every series of the experiment. Before the experiment, nine airflow velocity sensors were placed at nine points on the surface of the feed layer in order to measure the airflow velocity values of that nine points during the experiment. After the simulations and experiments, not only the simulation results of the airflow velocity distribution on the feed layer surface and experimental results of that were compared. but also the difference of airflow velocity distribution on feed surface between different feed layer thickness were compared. Results showed that the trend of airflow velocity distribution in simulation results and experimental results were consistent, which proved the simulations and experiments in this paper were reliable. Besides, the error between simulations and experimental results were also explained in this paper. According to the simulation and experimental results, aquatic feed layer thickness affected the airflow distribution inside the belt dryer and the airflow velocity distribution on the feed layer surface. When the feed layer thickness was 20 mm, the airflow velocity ranged from 0.6-1.3 m/s and the uniformity of airflow velocity distribution was not good. But when the feed layer thickness was 40 mm, airflow velocity ranged from 0.5-0.8 m/s and the uniformity of airflow velocity distribution was respectively good. The research in this paper provides theoretical guidance for the selection of feed layer thickness parameters in actual production of belt dryers, which can reduce the moisture content of aquatic feed and make the moisture content uniformity of aquatic feed good after drying. [ABSTRACT FROM AUTHOR]

A Biot number has been an excellent indicator for the heat or mass transfer performance during the agricultural production process. The difference between temperature and moisture can be determined between the inside and outside of the material, including heat transfer Bih and mass transfer Bim. Nowadays, a step-down relative humidity (RH) has been successfully applied to improve the drying efficiency and quality of some fruits and vegetables, such as carrots, American ginseng roots, and mushrooms. The high RH can be adopted in the step-down (RH) drying to pretreat the material, until the temperature increases to a high level. Afterward, the RH drying can be reduced to a low value for the surface moisture evaporation. The optimal angle of heat transfer can be selected for the high humidity in the early stage of step-down RH drying, leading to the rapid rise in the surface temperature. Once the surface temperature rises, the internal temperature increases in the way of heat conduction, and the migration and diffusion rate of water increases after the internal temperature rises. The mass transfer angle was also selected to inhibit the evaporation of water on the surface for the high humidity in the early stage, in order to prevent the surface from drying too fast and crust formation. Therefore, the difference between the surface and the internal temperature can be used to determine the dispersion and migration of the internal water into the surface in time, particularly for the effective dehumidification in step-down RH drying. The kind of fruit and vegetable materials can be the dominant factor in this case. It still remains unclear on step-down RH drying suitable for all fruit and vegetable materials. In this study, the applicability of step-down RH hot air drying was evaluated to clarify the drying characteristic, the effective moisture diffusion coefficient (Bih and Bim), color, rehydration ratio, and energy consumption of different thickness carrots (6, 12, and 18 mm) and logan under the step-down RH (first stage: 50% RH 30 min; second stage: 20% to end) and continuously dehumidification (RH<15%) with the drying temperature of 60 o C and the air velocity of 1.0 m/s. Results showed that the higher drying efficiency was achieved in the higher Deff value for the carrot and longan slices with the thickness of 6 mm in the continuous dehumidification, compared with stage one. By contrast, the stage dehumidification improved the drying efficiency with the higher Deff in the carrot slices of 12 mm or 18 mm. The Bih values of 6, 12, and 18 mm carrot slices were 0.582 7, 1.165 5, and 1.748 2, respectively. The maximum relative deviation was 2.7% between surface and internal temperature for the 6 mm carrot slices and Bim<1. The low RH greatly contributed to speeding up the drying rate, where the water inside the material was rapidly diffused to supply the surface. The maximum relative deviation between surface and internal temperature was 8.6% at the 12 mm carrot slices, and 13.8% at the 18 mm carrot slices, when Bim>1. Therefore, the step-down RH drying was necessary, due to the large water and temperature gradients on the surface and inside of the material. The Bim values of carrot slices with different thicknesses varied from 0.156 8 to 0.223 0. The Bim values of longan under the continuous dehumidification and step-down RH were 0.110 3 and 0.084 3, respectively. Furthermore, there was a small resistance of internal mass transfer in the longan (Bim<0.1), where the water quickly diffused to the flesh surface. Nevertheless, the flesh shrinkage, hard outer shell, and high RH outside caused great resistance to moisture migration during the drying process. The Bim values of carrot slices with different thicknesses were more than 0.1, indicating the large moisture gradient from the inside to the surface. Therefore, a high RH was adopted to reduce the evaporation rate of surface water for the high temperature. An excellent performance was achieved in the 6 mm carrot and longan under continuous dehumidification drying, indicating a better color, a higher rehydration ratio, and lower energy consumption. The carrot slices of 12 or 18 mm achieved better performance under step-down drying conditions. In conclusion, the applicability range of stage dehumidification drying was determined using heat and mass transfer Biot number, when Bih>1 and Bim>0.1 during step-down drying. The finding can provide theoretical and technical support for the different materials in the relative humidity control mode. [ABSTRACT FROM AUTHOR]

Revolutionary changes can take place in the energy field in the context of the dual carbon strategy. In particular, the energy conversion chain can be changed from the “heat generation by fuel and power generation by heat” to the “green power production and heat generation by electricity”, indicating the significant electrification trend of terminal energy consumption. Fortunately, the solar energy can be used to heat the refrigerant in the evaporator of a heat pump (called a direct-expansion solar-assisted heat pump system, DX-SAHP), where a solar collector can be employed as the evaporator. The heat pump system can be applied for the building heating to reduce the consumption of conventional fossil energy and pollution. But the intermittent and unstable characteristics of solar radiation have led to the reduction of solar energy utilization efficiency and operational reliability of the system. As a result, a control strategy can be widely expected for the safe, efficient, and stable operation of the system using the environmental parameters. In this study, a DX-SAHP operation control of the system was developed for the radiant floor heating platform with propane as the working medium in Qingdao, Shandong Province, China. The system was mainly composed of a micro-channel heat collector/evaporator with an area of 2.93 m², a constant frequency rotary compressor with the rated power of 732 W, an electronic expansion valve, a micro-channel condenser with a single surface area of 0.83 m² surrounding a 200 L water tank, a circulating water pump with a rated power of 46 W, and a radiant floor heating chamber with the heating area of 12.96 m² . The hot-water storage tank was directly connected with the radiant floor heating coil to transfer the heat into the heating chamber. The data of the control system was collected, including the solar radiation intensity, temperature, pressure, wind speed, flow rate, and power at the 5-second interval. The function of the control system was realized, including the start-stop control of the compressor, the start-stop control of the circulating water pump, and the opening control of the electronic expansion valve. An experiment was conducted to clarify the effects of solar irradiation intensity, ambient temperature, and supply water temperature on the thermal performance of the DX-SAHP for the radiant floor heating system. The operation control strategy was then proposed under the premise of indoor thermal comfort. The linear fitting of experimental data was utilized to obtain the lower limit of supply water temperature under various ambient temperatures. The water temperature inside the water tank increased to the set value, according to the actual demand for the heat storage of solar radiation. The superheat and discharge temperature of the compressor were controlled in a certain range for the safe operation of the system. The two-position control of indoor temperature was modified for the indoor thermal comfort condition with reduced energy consumption. The experimental results show that the DX-SAHP control strategy for the radiant floor heating system performed stable and efficiently under various working conditions, indicating a fully comfortable heating demand. The average coefficient for the performance of the system was between 2.02-3.58, the superheat of the working medium at the inlet of the compressor was stably maintained at 7-11, and the discharge temperature of the ℃ compressor was lower than 90 . A comparison was given for the indoor temperature and power consumption of the system ℃ with/without the control strategy. The heating effect of the system with the control strategy performed better than that of the without one, where the power consumption was reduced by 8.5%. The new control strategy was greatly conducive to the DX-SAHP system for the radiant floor heating system. [ABSTRACT FROM AUTHOR]

Automatic fruit picking has widely been popular for the intelligent estimation of orchard economic harvest in the field of smart agriculture. Object detection using deep learning has presented broad application prospects for spring-see citrus detection and counting. But, it is still a very challenging task to detect and count spring-see fruits, due mainly to the small size of spring-see citrus, the high density of fruit on a single spring-see tree, the similar shape and color of fruits, and the tendency to be heavily shaded by foliage. In this study, a YOLOv4 network model was proposed using a recursive fusion of features (FR-YOLOv4) for spring-see citrus detection. CSPResNext50 network with a smaller receptive field was also selected to detect small targets with higher accuracy. As such, the feature extraction in the original YOLOv4 object detection network model was replaced with the CSPResNext50 network, particularly for the small size of spring-see citrus. Therefore, the difficulty was reduced to greatly improve the detection accuracy of small-scale spring-see citrus, where the feature map of small-scale objects was easily transmitted to the object detector. In addition, the Recursive Feature Pyramid (RFP) network was used to replace the original YOLOv4 Path Aggregation Network (PANet), because of the fuzzy and dense distribution of spring-seeing citrus. Correspondingly, RFP networks significantly enhanced the feature extraction and characterization capabilities of the entire YOLOv4 network at a small computational cost. More importantly, the detection accuracy of the YOLOv4 network was improved for spring-see citrus in a real orchard environment. Additionally, a dataset was collected using images and videos of spring-see citrus captured in various environments in spring-see orchards. Subsequently, three data augmentation operations were performed using OpenCV tools to add Gaussian noise, luminance variation and rotation. The dataset was obtained with a total of 3 600 images, of which the training dataset consisted of 2 520 images and the test dataset consisted of 1 080 images. The experimental results on this test dataset showed that the average detection accuracy of FR-YOLOv4 was 94.6% for spring-see citrus in complex orchard environments, and the frame rate of video detection was 51 frames/s. Specifically, the average detection accuracy increased by 8.9 percentage points, whereas, the frame rate of video detection was only 6 frames/s lower, compared with YOLOv4 before the improvement. Consequently, the FR-YOLOv4 presented an average detection accuracy of 29.3, 14.1, and 16.2 percentages higher than that of Single Shot Multi-Box Detector (SSD), CenterNet, and Faster Region-Convolutional Neural Networks (Faster-RCNN), respectively. The frame rate of video detection was 17 and 33 frames/s higher than SSD and Faster-RCNN, respectively. Anyway, the YOLOv4 network model using a recursive fusion of features (FR-YOLOv4) can widely be expected to detect and count spring citrus suitable for actual complex environments in orchards, indicating a higher detection accuracy with real-time performance. [ABSTRACT FROM AUTHOR]

As long-standing goals and all-round development practices of agricultural and rural modernization of China, the rural revitalization strategy provides huge opportunities and spaces for the disciplinary innovation and development of all agricultural related disciplines. The purpose of this paper was aimed to analyze special requirements, objectives, tasks and implementation environment raised by the rural revitalization strategy, based on reviewing the references and development history of agricultural engineering, and to analyze impacts of the rural revitalization strategies on and demand for the adjustment of agricultural engineering innovation, so that to figure out the ways, means and measures for new round disciplinary adjustments and restructuring of agricultural engineering. In recent years, the disciplinary renovation and restructuring for all subjects have been encouraged and launched by the Ministry of Education, China. The new round adjustment of the discipline layout marked by the innovation and construction of new disciplines such as new engineering and new agriculture were given more attention on introducing new technological and industrial revolution achievements, and transforming and upgrading traditional engineering and agricultural science with information technology, digital technology and artificial intelligence. But it’s worth noting that insufficient attention had been paid to the expansion of agricultural and rural modernization roads and changes in development patterns caused by the rural revitalization in this important adjustment process. Agricultural engineering takes multiple and wide range responsibilities in offering scientific and technological support and talent training and cultivation, so that it plays a special and key role in the modernization of agricultural and rural areas. Information, communication, intelligent and smart technologies, and all new breaking through technologies should be introduced into agricultural engineering to equip and empower it more updated and effectively. Under such a background, more efforts should also be made in such important development consequences brought by the rural revitalization strategy. The disciplinary adjustment of agricultural engineering should be restructured and optimized according to the instructions of the national development strategies and its new application areas required by agricultural and rural modernization. The more attention should be paid to the influence of social and economic development mode and structural adjustment and upgrading on innovation and its correspondence. Great attentions should be paid to following key issues: 1) The implementation of the rural revitalization strategy has opened up some new development spaces for the disciplinary innovation of agricultural engineering and proposed new development requirements. 2) The development and extension of the agricultural engineering technology systems will extend from the agricultural production to rural multi-industrial integration, relying on all agricultural and rural resources. 3) The cultivation of agricultural engineering talents and the construction of educational scientific research systems should aim at the requirements of the whole process for all rural productions, as well for the construction of rural ecological systems. 4) The systematic construction and management of agricultural and rural industries in different regions should meet the needs of the urban-rural integration development and the modernization of new rural communities’ governance system. Currently, more reform, renovations and adjustments should be made to reshape the agricultural engineering to meet new needs of the rural revitalization, the new development fields and directions of agricultural engineering disciplinary innovation currently are more practical in rural e-commerce engineering, rural landscape construction and maintenance engineering, rural new industrial development space construction, rural ecological environment engineering, and rural social and economic management and governance system engineering. [ABSTRACT FROM AUTHOR]

Large rainfall fluctuation and excessive nitrogen application are the main factors that limit the nitrogen fertilizer efficient utilization and stable yield and high quality in winter wheat production in Weibei dryland. In this study, the purpose was to construct different critical nitrogen concentration dilution curves of winter wheat under two precipitation patterns to analyze the feasibility of diagnosing the nitrogen nutrion status of dryland winter wheat by the nitrogen nutrient index. From 2017 to 2021, a 4-year nitrogen application test was conducted in Heyang County, Shaanxi Province, with Jinmai 47 as the test material. Five nitrogen application rate treatments were set at 0, 60, 120, 180 and 240 kg/hm2 . According to the classification of precipitation patterns, normal years were 2017-2018 and 2020-2021, and dry years were 2018-2019 and 2019-2020. The effects of different nitrogen application rate on nitrogen utilization efficiency, grain yield and its components of winter wheat under the two precipitation patterns were srudied. Based on the relationship between the aboveground biomass and plant nitrogen concentration of winter wheat in dryland under the two precipitation patterns, the critical nitrogen concentration dilution curve model and nitrogen nutrient index (NNI) was established. The results show that: 1) nitrogen application, precipitation patterns and their interaction effects have a significant impact on the grain number per spike, 1 000-grain weight and grain yield. 2) The aboveground biomass and critical plant nitrogen concentration of winter wheat under normal years and dry years were conform to the power function relationship. However, there are variances in models parameters of normal years and dry years(the model parameter a were 3.33 and 2.79 g/kg in normal and dry years, and the parameter b was 0.40 and 0.31 in normal and dry years, respectively). The model validation showed that the plant nitrogen concentration fitted by the critical nitrogen concentration dilution curve model was linearly correlated with the actual nitrogen concentration. The root mean square error (RMSE) was 0.20 and 0.14 g/kg in normal years and dry years, respectively, and the normalized root mean square error (NRMSE) was 10.30% and 7.69%, respectively, indicating that models had good stability. 3) According to the grain yield and nitrogen nutrition index, the appropriate nitrogen rates in normal and dry years was 160-180 kg/hm2 and 101- 120 kg/hm2 . In this study, the critical nitrogen concentration dilution curve and nitrogen nutrient index were established based on the aboveground biomass and plant nitrogen concentration of dryland winter wheat during each growth states under the two precipitation patterns. The critical nitrogen concentration dilution curve and nitrogen nutrient index better predicted the nitrogen nutrient status of winter wheat in different growth stages under the two precipitation patterns. The results can provide valuable information for the nitrogen assessment and precise nitrogen application. [ABSTRACT FROM AUTHOR]

The fuel spray performance and atomization quality played a fundamental role in promoting the level of combustion efficiency and exhaust emissions in internal combustion engines. In order to achieve better atomizing mode of diesel, we conducted experiments to study the spray characteristics of diesel blending pine oil. A diesel/pine oil spray trial platform was constructed to carry out a visual constant volume chamber and the high-pressure common rail test bench. The high-speed photograph technique was applied to systematically investigate the spray process of blended fuel. The study was conducted under the pine oil blending ratios of with 0, 20%, 40% and 50%, respectively. Then, the influences of injection pressure, ambient pressure and fuel property on macroscopic spray parameters (including spray cone angle, spray penetration distance and fuel flow area) were investigated. The results showed that at first, the spray penetration distance of blended fuel presented a certain degree of linear growth with the fuel injection, and then the increasing rate of the penetration distance decreased. On the other hand, it was observed that the spray cone angle was wider at the beginning of the spray development, and it gradually converged to a smaller and constant value. In general, the variation of the spray cone angle is stabilized during spray process. For the same ambient pressure (5 MPa), the blended fuel had a longer penetration distance with increasing the fuel injection pressure from 90 MPa to 150 MPa. And the effect of injection pressure on the spray cone angle according to the variation in injection pressure showed that the spray cone angle at a 150 MPa injection pressure was larger than that at 90 MPa of injection pressure. The percentage increased in the mean spray cone angle and penetration distance was 9.2% and 15%, respectively. When the ambient pressure increased from 3 MPa to 5 MPa at the same injection pressure (12 MPa), the increment of ambient pressure led to obvious increase of the spray cone angle as well as sharp decrease of the penetration distance. During the spray evolution process, the mean spray cone angle increased about 2.6°. The spray penetration distance decreased about 11 mm at the end of the injection. This indicated that the rise of ambient pressure had a significant effect on spray characteristics. In the range of experimental condition, good correlation was found between the spray penetration distance of blended fuel and the modified Hiroyasu's empirical equation. When injection pressure was 150 MPa and ambient pressure was 5 MPa, the effect of Reynolds number was greater than that of Weber number as blending ratios of pine oil increased by 50%. This suggested that the fuel viscosity played an important role in spray characteristics. The spray performance of blended fuel was basically similar to conventional diesel fuel with the variation of injection pressure and ambient pressure. In addition, analyses showed that the spray penetration distance, spray cone angle and fuel flow area increased slightly after blended a certain proportion of pine oil into diesel, which was very conducive to improve air and fuel mixture effect with pine oil. It can be concluded that investigating the spray characteristics of diesel and pine oil blends would be significantly beneficial for enhancing the atomization quality of pure diesel, and also provided a valuable reference on the spray characteristics to choose an acceptable and appropriate alternative fuel for common rail diesel engine. [ABSTRACT FROM AUTHOR]

It is important for policy-making of irrigation to better understand if the irrigation area is overloaded. In this study, we explored the irrigation area overloading problem in basins of Tarim River in China in 2010 and 2020. The study focused mainly on four rivers and one mainstream in the Tarim River. The affordable irrigation area was calculated as the ratio of maximal irrigation amount for agriculture and gross irrigation quota. The available irrigation amount for agriculture was determined by subtracting water for lives, livestock, industry, ecology and discharged water to mainstream from total water amount. The data of irrigation area, gross irrigation quota, irrigation amount for lives, liverstock, and industry in 2010 were collected by investigation and provided by local administration. Those in 2020 were obtained according to an integrated management plan of Tarim river. Water for ecology was from previous studies. The overloading area was defined as the difference of real or planned irrigation area and maximal irrigation area. The results showed that: 1) There was a total of 17.1×105hm2 irrigation area in four source streams and mainstream of Tarim River in 2010, while the maximum area allowed was only 12.9×105 hm2, suggesting an overloaded area of 4.33×105 hm2 that was about 33.6% overloaded; Except for the Hotan-river basin, the others basins such as Yarkant-river, Aksu, Kaidu river-kongque river and the main stream of Tarim River were overloaded by 0.87×105, 1.41×105, 1.65×105 and 0.40×105 hm2, and corresponding to an overloading percentage of 21.0%, 35.2%, 84.6% and 66.7%; 2) In 2010, four basins were overloaded, but only three in 2020; in 2020 the overloading of the four source streams and mainstream of Tarim River decreased 2.98×105 hm2 with the percentage of 68.86% compared with that in 2010; But the overloading was serious in basins of Kaidu river-kongque river and the mainstream of Tarim River with the overloading rate of 31.6% and 34.0%, respectively; 3) There were two main reasons for the increasing of environment capacity in 2020: one was the improvement of the level of water utilization, the irrigation quota in basins of Hortan river, Yarkant river, Aksu river Kaidu river-kongque river and the main stream of Tarim River in 2020 were decreased by 12.4%, 15.8%, 18.0%, 11.6% and 9.9%, respectively compared with that in 2010; the other reason was the reduction of planning irrigation area since the planning irrigation area in basins of Aksu river, Kaidu river-kongque river and the mainstream were reduced by 0.64×105, 1.23×105, and 0.01×105 hm2, respectively. The study can provide data support for irrigation plan of the Tarim river basin. [ABSTRACT FROM AUTHOR]

In order to make a reasonable control strategy of Reactivity Controlled Compression Ignition (RCCI) combustion mode and to explore the influence of different combustion boundary conditions on the combustion and emission characteristics of RCCI, in this paper, a six-cylinder heavy-duty diesel engine was used to test the RCCI of gasoline / diesel dual fuel under the condition of constant engine speed and gasoline energy Premixing Ratio (PR). The effects and its degree of Start of Injection (SOI) and Inlet Pressure (IP) on gasoline/diesel RCCI combustion and emission characteristics were studied under different Cycle Energy (CE) operating conditions with a fixed gasoline energy PR of 65%. The results indicated that the effects of SOI and IP on all combustion characteristic parameters hardly changed with the increase of CE. For example, the ignition delay increased with the advancement of SOI under different CE. The effects degree of SOI and IP on some combustion characteristic parameters changed with the increase of CE. For example, with the same advancement of SOI (23 °CA), the maximum of cumulative heat release was average increased by about 150 J when CE was 885 J, while the maximum of cumulative heat release was average increased by about 250 J when CE was 1 700 J, the effects degree of SOI on maximum of cumulative heat release became greater with the increase of CE. What’s more, the adjustment range of IP on the peak average temperature in the cylinder was decreased by about 130 K, when CE increased from 885 to 1 700 J, the effects degree of IP on the peak average temperature in the cylinder became greater with the increase of CE, which indicated that the adjustment capacity of IP on the in-cylinder temperature became stronger. However, the effects degree of SOI and IP on some combustion parameters did not change with the increase of CE, such as the effects degree of SOI and IP on the ignition delay, the increase of the ignition delay was almost the same (about 10 °CA) with the advancement of SOI (23 °CA) under different CE. What’s more, the change of thermal efficiency was almost the same (about 5%) with the advancement of SOI (23 °CA) under different CE. Besides, the effects of SOI and IP on the gas emissions, except the CO emission, almost unchanged with the increase of CE. In fact, when CE increased from 885 to 1 700 J, the CO emission decreased continuously. However, the increase of CE changed the effects degree of SOI and IP on some gas emissions, for example, with the same increase of IP by 15 kPa, the HC emission was average increased by about 13.65 g/(kW·h) when CE was 885 J, it remained almost the same with the CE was 1 700 J, that was, the effects degree of IP on the HC emission was greatly reduced with the increase of CE, which indicated that the adjustment capacity of IP on the HC emission became weaker. What’s more, with the same increase of IP from 110 to 125 kPa, the NOx emission was average decreased by about 1 g/(kW·h) when CE was 885 J, while the NOx emission was average decreased by about 4 g/(kW·h) when CE was 1 700 J, that was, the effects degree of IP on the NOx emission was slightly increased with the increase of CE, which indicated that the adjustment capacity of IP on the NOx emission was slightly enhanced. In addition, the increase of CE changed the effects or its degree on some parameters of particles emission. For example, the effects degree of SOI and IP on the average particle size and number concentration of nuclear particles were both decreased with the increase of CE, which indicated that the adjustment capacity of SOI and IP on the nuclear particles became weaker. On the contrary, the effects or its degree of some parameters of particles emission did not change with the increase of CE. For instance, the impact of SOI on the total mass concentration of particles was almost the same under different CE. The research results can provide data support for making a reasonable control strategy of RCCI combustion mode. [ABSTRACT FROM AUTHOR]

Reactivity control compression ignition (RCCI) has been shown to be effective in reducing nitrogen oxides (NOx) and particle matter (PM). A significant feature of RCCI is the ability to control the combustion process by creating reactivity stratification in the cylinder, which could reduce emissions. Since iso-butanol has a higher octane number, it can enhance the gradient of reactivity stratification, which will facilitate the control of combustion. The effect of iso-butanol on engine combustion and emission characteristics was investigated on a six-cylinder turbocharged diesel engine under RCCI combustion mode. In this study, iso-butanol (low reactivity fuel) was provided through the port injection (PI), and the diesel (high reactivity fuel) was injected directly into the cylinder. In the test, the combustion and emission characteristics of RCCI fueled with iso-butanol and diesel were investigated with different fuel supply strategies by changing the premixing ratio (Rp) of iso-butanol and the start of injection (SOI) of diesel under low engine load. Four different premix ratios were selected, including 30%, 40%, 50% and 60%, and five different SOIs were designed, including -8°, -12°, -18°, -24° and -30°crank angle after top dead center (°CA ATDC). In this study, the engine was operated at a constant speed of 1 500 r/min, maintaining the brake mean effective pressure (BMEP) and the total cycle energy at 0.3 MPa and 1 280 J, respectively. The results showed that, with the advancement of SOI, the ignition delay (ID) was prolonged and the maximum heat release rate (HRRm) was increased first and then decreased. In terms of emission characteristics, with the advancement of SOI, the emission level of THC and CO decreased, and NOx emission increased first and then decreased. As SOI was further advanced to -30 °CA ATDC, it can be seen that the emission of CO increased when Rp was 30% or 40%. While the emission of PM at Rp from 30% to 50% showed a trend of decreasing first and then increasing, when Rp was 60%, it only showed a decreasing trend. In addition, the Rp of iso-butanol also had a large effect on RCCI combustion and emission characteristics. As the Rp increased, both the ID and CD (combustion duration) increased, while the HRRm decreased. In terms of emission characteristics, THC and CO increased and NOx decreased with the increase of Rp. When Rp was 30%, the total PM mass achieved the highest level under the four different Rp, and when Rp was 60%, it had a lower level of the total PM mass than that when Rp was 40% or 50% and SOI was -30 °CA ATDC. The size distribution of PM showed that the quantity of nuclear particle matter (PMN) was dominant, of which the diameter size was in the range of 3-30 nm. However, the proportion of PMN was very small for the total PM mass. In the mass concentration, the PM mass was dominated by the accumulated particle matter (PMA), of which the diameter size was in the range of 30-500 nm. The increase in the Rp reduced the whole PM quantity, but with the SOI advanced, the PMN quantity increased first and then decreased, while the PMA quantity decreased first and then increased, except when Rp was 60%. When Rp was 60%, PMA quantity only showed a decreasing trend with the advancement of SOI. The Rp had a complex effect on the mass distribution of PM. The most interesting part was that, when Rp was 60%, the total PM mass was higher than that when Rp was 40% or 50% at SOIs near the top dead center. The reason was that, when Rp was 60%, the peak value of PMA quantity was lower than that when Rp was 40% or 50% in the range of 30-500nm, whereas in the range 100-200 nm, more PMA quantity was exhibited, which lead to higher total PM mass. In addition, as the SOI advanced, the mass of PM generally showed a decreasing trend. [ABSTRACT FROM AUTHOR]

Grain cleaning is the core technology of peanut harvest. Therefore, in the process of peanut harvesting, how to enhance operation fluency and efficiency, and to ensure technical indicators such as low loss rate of cleaning, low impurity rate of peanut pods, has been a difficult technical problem of whole-feed peanut combine harvester. In order to settle the above difficulties, a cleaning device of tangential flow and whole-feed peanut combine harvester was designed, realizing the grain winnowed combined with screened, one-time large and small sundries clearance, sieve surface unencumbered. The cleaning device of tangential flow and whole-feed peanut combine harvester consisted of pole sieve, multi-stage elastic sieve, behind sieve, straw-shaking wheel, eccentric sleeve, main fan, auxiliary fan. The vibrating sieve consisted of pole sieve, multi-stage elastic sieve, behind sieve. Pole sieve was above the vibrating sieve. Multi-stage elastic sieve and behind sieve were below the vibrating sieve. Combined with existed mechanism advantages, a crank-rocker mechanism which consisted of the vibrating sieve and swinging arm was brought forward. In the application of cleaning device of tangential flow and whole-feed peanut combine harvester, there are many problems such as high impurity rate of peanut pods, high loss rate of cleaning, agricultural film tangles, and debris blockage. Utilizing kineto-statics method, in this paper, we researched relative motion of grain on the sieve surface, analyzed limiting conditions of grain upglide, downglide, jump from sieve surface, and determined the key motion parameter in theory. Vibration acceleration of vibrating sieve was 17.5-24.5 m/s2. Amplitude of vibrating sieve was 7.5-17.5 mm. Vibration frequency of vibrating sieve was 5-9 Hz. Utilizing D'Alembert's principle, in this paper, we also researched sieve force under alternating loads, determined the important structure parameter of sieve. Cleaning device was matched onto the whole-feed combine and a lot of tests were carried out in the field. Loss rate of cleaning and impurity rate of peanut pods were taken as the evaluation indicator of cleaning quality. The key factors affecting cleaning quality were researched by field experiment in this paper. A scheme of orthogonal test, which included 3 factors and 3 levels, was designed. That key factor included amplitude, vibration frequency and revolving speed of main fan. The value range of amplitude and vibration frequency was based on the preceding theoretical analysis. The value range of revolving speed of main fan was based on single factor experiment. The experimental results showed that significant order for multi-factors affected on cleaning quality was: revolving speed of main fan, amplitude, vibration frequency. Within the scope of the 95% confidence coefficient, revolving speed of main fan was extremely significant for cleaning quality, amplitude and vibration frequency were significant for cleaning quality. The optimal parameter combination was that revolving speed of main fan was 2 100 r/min, amplitude was 12.5 mm, vibration frequency was 9 Hz. Under the above optimal parameters, field experiments were carried out, loss rate of cleaning was 5.03% and impurity rate of peanut pods was 5.39%. The operation of cleaning device is fluent, almost no agricultural film tangles and debris blockage. The research results provide theoretical basis for design and parameter optimization of whole-feed peanut combine harvester and cleaning device [ABSTRACT FROM AUTHOR]

Vegetation types affect process of runoff, soil erosion and nutrient transport along loess slope land. In order to clarify the influence of vegetation types on surface runoff, sediment transport and nutrients in loess region, a field water scouring experiment was performed on a natural, fallowed loessial slope (38°46′-38°51′N, 110°21′-110°23′E) on 14 km west of Shenmu Erosion and Environment Research Station of Institute of Soil and Water Conservation, Chinese Academy of Sciences, in the Liudaogou watershed, Shenmu County, Shaanxi Province at Shenmu. A steady-head water scouring method was adopted under natural conditions. Field plots were established on a slope that had been fallowed for 7 years. Herbaceous and crops were selected as vegetation types, including maize, millet, soybean, cymbaria dahurica, alfalfa and caragana. Runoff, sediment, and nutrients (nitrogen and phosphorus) under different vegetation cover were determined. In addition, basic growth characteristics of various vegetations in each plot were measured. Results showed that compared with the other vegetations, the effect of herbaceous (cymbaria dahurica) on the decrease of surface runoff was largest, and soybean was the lowest. With vegetation cover, less sediment was carried with by runoff, the process of sediment appeared a peak for all the vegetation cover, and alfafa cover significantly decreased sediment loss. Under different vegetation covers, the concentration of nitrate nitrogen and soluble phosphorus in runoff water decreased rapidly at the initial runoff stage, and then to be stabilized. The process of nutrients (nitrate nitrogen and soluble phosphorus) transport could be better described with power function than exponential function. Results also revealed that the amount of nitrate nitrogen in sediment decreased rapidly, while the amount of effective phosphorus in soil reduced gradually over time. When soil surface was covered with alfalfa, and the total loss of nitrate nitrogen and phosphorus in sediment was highest. It could also be found that nutrients enrichment ratio had a reverse relationship with erosion amount for the all vegetation cover. The total loss of nitrate nitrogen under different vegetation cover was highest in millet cover, followed by alfalfa, caragana, maize, soybean, and cymbaria dahurica, and the total loss of soluble phosphorus was highest in millet cover, followed by maize, caragana, soybean, cymbaria dahurica and alfalfa. Nitrate nitrogen showed a peak feature along depth in soil profile, and the peak position was different for different vegetation covers. Phosphorus was mainly cumulated at the top 5 cm of the surface layer, and the amount of phosphorus was extremely low below 5-cm soil depth. In conclusion, the effects of herbaceous cover on surface runoff, sediment transport and the loss of nutrients were much better than crop cover. This study provides a way for further analyzing the effect of vegetation cover on water and soil nutrient loss, and provides a guide for controlling soil water loss and agricultural management. [ABSTRACT FROM AUTHOR]

With the rapid development of marine aquaculture industry, the amount of wastewater discharged is increasing and the water environment in the coastal areas is seriously deteriorated.Because of high concentration of total suspended matter; the content of soluble organic matter and inorganic matter in marine aquaculture wastewater is huge, whichresult indifficulties for treatment.In order to protect the marine environment and reduce the disease spread, the treatment of intensive aquaculture wastewater has become an inevitable trend.However, mariculture wastewater is more difficult to treat than that of freshwater, because of the effects of salinity, especially on membrane's microbeeinhibition and contamination mitigation.In this paper, activated sludge within membrane bioreactor(MBR) disturbed by mariculture wastewater was investigated, during and after salt shock, meanwhile, effect of powdered activated carbon(PAC), was examined in parallel lab scale MBR, particularly on their contaminant removal performance and membrane fouling influence, within the salinity ranging from 0 g/L to 35 g/L.Concentration of chemical oxygen demand(COD), ammonia nitrogen(NH+4-N) and nitrite nitrogen(NO2-N) were analyzed emphaticallyunder the long term effect of macriculture wastewater, besides,variation of microorganism properties, membrane flux, and floc particle size were studied.Particularly, salinity changes range from 0 g/L to 5 g/L were selected to analyze corresponding,composition and concentrationchanges of the dissolved organic matter in bulk solution soluble microbileproducts, SMP and sludge flocs extracellular polymers substances(extracellular polymeric substances, EPS), which could help to explain the relationship between the hydrophobicity of sludge and polysaccharide, protein.The results showed that PAC could improve the anti fouling ability of membrane, i.e.For MBR PAC,The COD removal efficiencyis 7.3% higher than that of MBR,combined with better removal stability of NH+4-N and NO2-N.For MBR,the fluctuation of removal of NH+4-N and NO2-N was more obvious.In the process of salinity changes, the membrane flux of two parallel lab scales presented a similar trend, in detail, the flux declined in the sensitive period andrecovered to a certain extent in stationary phase.However, the recovery period of MBR PAC system was shorter than that of MBR, the change of flux is moreobvious in MBR.In result, the membrane flux under MBR PAC system could be improved remarkable, which showed about 1.5 times than that of MBR, in the end, the flux of MBR was lower, and the membrane of MBR could be damaged.During the salinity changing process, PAC could increase the sludge relatively hydrophobic (RH) and average floc sludge particle size, at the same time, adsorption and flocculation ability of PAC would contribute the reduction of microbial metabolites, particularly for small molecular protein,obtaininga 34% reduction.At the end of operation, the sludge mean particle size of MBR PAC waslarger, and the value increased 52 μm than that of MBR.Conclusions could be made that introduction of PAC is a useful mitigation strategy for MBR.Slow down membrane fouling rate.MBR PAC is suitable for mariculture wastewater treatment, and the treatment effect is superior to MBR. [ABSTRACT FROM AUTHOR]