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Soil wind erosion is the main cause of land degradation in arid and semi-arid areas in northern China, which is mainly affected by surface type, climate and so on. Strong soil wind-erosion will not only accelerate regional desertification and influence the quality of human life, but also cause serious ecological and environmental problems. Since the 2000 s, our country has gradually strengthened the control of land desertification and carried out a series of sand control works, which effectively improved the overall ecological environment of the sandy land. But in recent years, there are some common phenomenon that extensive grassland and brushland was turned into cultivated land in the southeast and southwest of Mu Us sandy land. However, in the dry and windy winter or spring, these new reclaimation land is usually so exposed that it is vulnerable to suffer from strong wind erosion. Therefore, it is great significance to study the characteristics of soil wind erosion in new reclaimation land and find out the control methods. Based on the above question, this paper selected the southern part of Mu Us sandy land (38°05′27″-38°13′58″N, 107°24′28″-107°37′30″E) as the research area, as well as set up 5 observation points on different surfaces, which were represented respectively by A, B, C, D and E. Point A was on the brushland, point B was on the middle of the grassland, and other three points were respectively on different parts of the cultivated land. On the day with strong wind activity, 12 groups simultaneous observation of wind and sand were made at these 5 points (A, B, C, D, E), with each observation time at least 20 minutes. After these observations, the material of the sand samplers were weighed with an electronic balance of 1/1 000, and the material of surface and sand samplers on cultivated land were analyzed by Mastersizer2000 Laser Particle Size Analyzer. The results showed that the soil wind erosion intensity increased exponentially after grassland and shrubland were cultivated; on cultivated land, with the increase of height, the sediment transport rate decreases with exponential function within 0-10 cm height and power function within 10-20 cm height. Due to the height of the sand collector used in this paper is 20cm, lower than the height of the sand flow layer. In order to obtain the total sediment transport rate of the surface of the cultivated land, this paper must calculate it through the function simulation obtained from the above result. After calculating the total sediment transport rate, fitting it with the wind speed. We found that the total sediment transport rate has a good power function relationship with the wind speed in the cultivated land with sufficient erodibility particles. Based on the formula of the relationship between wind speed and total sediment transport rate, as well as the wind speed data of the meteorological stations in the region, the wind erosion modulus of the new reclaimation land can be preliminarily calculated. The result shows that the wind erosion modulus of the new reclaimed land is 9 657 t/(km2·a). Through the results obtained in this paper, combined with the former research results, this paper argues that the emergence of new reclaimed land has an important impact on regional desertification, and its area should be used as an important index when evaluating regional desertification. Meanwhile, Controlling cultivated land area, establishing windbreak and sand fixation forest, as well as retaining stubble at a certain height can effectively control soil wind erosion in newly reclaimed land. [ABSTRACT FROM AUTHOR]

Freshwater and energy are indispensable resources for human survival and social developments. However, fresh water scarcity is expanding and intensifying around the world because of rapid population growth, industry development, abnormal climate and urbanization. Especially, the shortage of useful water has become more obviously for isolated or arid regions. Great amount of groundwater in these regions found in wells usually remains brackish water. To obtain safe and pure drinking water, various brackish water distillation technologies have been increasingly recommended as a viable alternative. However, conventional distillation processes have indicated highly energy consumption, and potential environmental impacts due to the utilization of fossil fuels. It is necessary to utilize solar energy for the brackish water distillation, in order to meet the high requirement of potable water and agriculture in the remote and arid regions blessed with ample amount of solar energy. This paper therefore designed a novel multi-effect solar brackish water distillation device based on vertical tube falling film, which allows testing of four operational modes, i.e., single-effect, double-effect, triple-effect and four-effect. Compared with conventional solar brackish water distillation device, some advantages can be achieved, such as falling film evaporation, multi-effect operation, smaller thermal resistance, and higher efficiency of thermal utilization. The working principle was introduced for the four-effect device and structure. A theoretical analysis of heat and mass transfer process of the device was carried out. The water yield, evaporation temperature and condensation temperature of the device for four operation modes were tested under the fixed heating power operation. The effects of the different operation effects on the water yield per energy and GOR (Gain Output Ratio) were investigated, together with the economic analysis of the multi-effect devices. The results demonstrated that when the heating power was 200W, the water yield per energy and the total water production of the four-effect device were 1.45 g/kJ and 1.039 kg/h, indicating an increase by 36.80% and 35.88% than that of the triple-effect device, respectively. The steady-state operation temperature was 83.76 ℃, while the total temperature difference of evaporation and condensation was 19.07 o C in the four-effect device. The GOR of four-effect device can reach 3.36. The payback period of four-effect device was 5.69 years. Performance and economic analyses of the devices indicated a wide applicability of the system, especially for remote and arid regions. [ABSTRACT FROM AUTHOR]

Drought is a natural hazard caused by long-term precipitation deficiency and high evaporation resulted from high temperature, which is among the most common disasters around the world. In recent decades, with the intensification of climate change and human activities, drought occurrence is becoming more frequent in China, causing negative impacts on agricultural production, ecological environment and social economy. Therefore, it is significant to explore the impact of drought on vegetation for agricultural production and healthy development of ecological systems. In this paper, the response and sensitivity of vegetation to drought in different climatic zones in China were analyzed, and the effects of different climatic factors, including water balance (precipitation-potential evapotranspiration), annual precipitation, mean temperature and sunshine hours, on the relationship between different vegetation types including forestland, grassland and cultivated land and drought were explored, so as to reveal the response mechanism of ecological vegetation to drought from a macro perspective. Using the self-calibrating Palmer drought severity index (scPDSI) and normalized difference vegetation index (NDVI) data for the period of 1982-2015, the response rule and sensitivity of different types of vegetation to drought were analyzed by applying time-delay correlation method, and the influence of various climate factors on the relationship between vegetation and drought was analyzed by applying linear regression method. The results of the research showed that in northwest China, Inner Mongolia, north China plain and southern Qinghai-Tibet plateau, the correlation of shorter lag time scPDSI (1-3 months) and NDVI was close (Rmax>0.4), which indicated that vegetation growth was more sensitive to drought in these regions and that vegetation biomass were influenced mainly by the spatiotemporal characteristics of the water availability. In the humid areas of south China, including the middle and lower reaches of the Yangtze River and the Pearl River basin, the precipitation is abundant so that the correlation between NDVI and scPDSI was negative, and the response of vegetation was not sensitive to drought. The growth of vegetation is mainly controlled by energy factors such as temperature and sunshine hours. The relationship between vegetation and drought was significantly affected by the average annual water balance, precipitation, sunshine hours and temperature, among which the annual water balance was the main water controlling factor (R²=0.45). It can be concluded that the change of water availability was the key factor behind the change of vegetation vigor. Sunshine hours were the main energy controlling factor. When average annual temperature was less than 5, the effect of ℃ temperature on the correlation between scPDSI and NDVI was also significant. The sensitive areas of drought impact on vegetation were mainly in the northern arid regions, while the southern humid areas had strong resilience and resilience to drought. The sensitivity of different types of vegetation to drought varied greatly, and the order of sensitivity is grassland >forestland>cultivated land. The results can provide a scientific basis for the evaluation of the impact of drought on ecological vegetation in different regions of China, and thus help to guide agricultural and environmental production, protect vulnerable ecosystems and provide implications for sustainable socioeconomic development. [ABSTRACT FROM AUTHOR]

Corn is one of the main grain crops in China, and it is also an important part of farmers' income source. In recent years, in order to achieve the goal of increasing agricultural maize income, corn planting areas in the middle east of Gansu have used a technology called the double-furrow sowing with whole plastic film against the drought, and it provides an effective technical approach for a steady increase in the yield of maize in arid regions. According to statistics, by the end of 2013, the rate of corn mechanical harvest was 49%, and till 2016, the rate of corn mechanical harvest reached 63% in China. On the whole, the corn mechanization level in China has been greatly improved, but the harvest of maize in Gansu Province is mainly based on artificial harvesting, and mechanized harvest has lagged behind the national average level. Except some small plots that can not use combine harvester, plastic film has become one of the main reasons limiting the application of corn combined operation machinery. If we continue to use the machine with horizontal roller commonly used in China at present for harvesting, then after stripping the collection process of corn stalk can not be completed. Therefore, the ordinary type of corn combine harvester with horizontal roller is not suitable for agricultural production in arid regions. To adapt to the cropping patterns of the whole plastic film and double-furrow sowing in arid regions, and solve the problem that the corn plant can not be fed continuously into the header of the harvester during the harvesting process, as well as the high loss rate issue of traditional corn harvester, a kind of self-propelled corn combine harvester for harvesting ear and stalk was designed in this paper. This machine cut 2 rows at one time, and used the vertical snapping rolls to grab the corn ear from the corn stalk, and the corn ear was delivered at the middle of the cutting platform; behind the vertical snapping rolls there was a shredding device, and the corn stalk chopped by the shredding device was conveyed by the conveyer on the side of the combine harvester. This arrangement on the cutting header realized whole plastic film mulching on double ridges for two-row cutting and reaping both corn ear and stalk for corn combine harvester, and grain loss was reduced. Because of the existence of plastic film, the corn stalk after picking could not be smashed and returned to the field with corn stubble. However, the vertical snapping rolls could solve this kind of defect. When the vertical snapping rolls worked, the stalk was output from the vertical snapping rolls, so it was suitable to recycle the stalk. Compared with the horizontal snapping rolls, the vertical snapping rolls can reduce the weight of the cutting platform and shorten the length of the machine. At the same time, the turning radius is reduced correspondingly, the turning is more flexible, and the machine can walk better on the double ridges. In addition, the gripping delivery mechanism adopts a holding and convey chain on one side, and the other side is an eccentric elastic tooth type shifting wheel, so the weight of the cutting platform is further reduced. And the machine can complete the function of corn ear's picking, conveying, peeling and collecting at one time, as well as the stalks cutting, kneading, chopping, throwing and collecting. The field experimental results showed that the grain loss rate was 1.8%, the ear loss rate was 2.4%, the grain damage rate was 0.77%, the qualified rate of cutting corn stalk was 92.6%, and the husking rate of corn was 95.1%, when the machine speed was 4.5 km/h, the speed of vertical snapping rolls was 1 100 r/min, and the speed of shredding device was 1 584 r/min. And the experimental results meet the design requirements of combined operation machine. [ABSTRACT FROM AUTHOR]