Influence of grain discharge rate on the normal force of arch

The arch stress of grain particles during the discharge of the silo is very important to the safety of the silo. At present, most silos adopt the standard discharge port size. To improve the discharge efficiency, it is generally achieved by changing the angle of the discharge port. In this article, an improved silo model is used to study the discharge experiments in the silo with five inclination angles of the discharge port, and analyze the normal force distribution of the wheat grains at the arch, comparing the normal force distribution under five different discharge rates. From the results given, when the angle of the discharge port is 45°, the area where the normal force among particles is larger is wider. At other flow rates, increasing the flow rate can shorten the arching period. During the arching cycle, the normal force among particles in the center area of the silo at the same height is smaller than at the silo wall and is negatively correlated with the discharge rate. In addition, the normal force on the silo wall gradually decreases with the increase in the discharge rate

Natural and semi-natural land dynamics under water resource change from 1990 to 2015 in the Tarim Basin, China

The Tarim Basin is a typical arid area and has the world’s most severe desertification of natural and semi-natural land due to limited water resources. However, knowledge about the impacts of changes in water resources on the spatio-temporal dynamics of natural and semi-natural land is still limited. We analyzed the spatio-temporal changes in natural and semi-natural land and the associations with desertification in the Tarim Basin during the period 1990–2015. We then investigated the changes in water resources and the consequent impacts on the spatio-temporal changes of natural and semi-natural land by integrating Gravity Recovery and Climate Experiment territorial water storage data and field observations. The results showed that a total area of 10.32 × 10 ^3 km ^2 of natural and semi-natural land was converted to desert during the period 1990–2015. Desert vegetation type and saline type were the natural and semi-natural land types most sensitive to conversion to desert. The area of natural and semi-natural land decreased by 0.83% every year, and the proportion of desertified land was 34.79% on average during the period 2000–2010; this is less than for the period 1990–2000 (1.14% yr ^−1 and 52.01%) due to increased availability of water resources from the water conveyance program. However, the rate of decrease of natural and semi-natural land area (0.93% yr ^−1 ) and the proportion of desertified land (58.88%) rose again during the period 2010–2015 due to the rapid decrease in water resources. During the period 2000–2015, the rate of loss of natural and semi-natural land area (7.89%) in the region with decreased water resources was about twice that in the region with increased water resources (3.88%), highlighting the critical role of water resources in maintaining natural and semi-natural land and slowing desertification

Micro-Volume Blood Separation Membrane for In-Situ Biosensing

In this paper, we report a point-of-care (POCT) testing strip based on a porous membrane structure for whole blood separation and colorimetric analysis without external supporting equipment. Conventional blood tests rely on large instruments for blood pretreatment and separation to improve measurement accuracy. Cellulose acetate (CA) membranes with different pore diameters and structures were prepared via a non-solvent method for the separation of whole blood. Among them, CA@PEG-2000 membranes with nano-pores on the surface and micro-pores in the interior facilitated the capture of blood cells on the surface, as well as the free diffusion of plasma through the porous interior structure. The fluid flow of blood in the asymmetric porous structure can be theoretically estimated using the Lucas-Washburn equation. Compared with the conventional paper strips and other porous membranes, the CA@PEG-2000 membrane with an immobilized sensing layer exhibited efficient blood separation, a short response time (less than 2 min), an ultralow dosage volume (5 μL), and high sensitivity. The fabricated blood separation membranes can be further used for the detection of various biomarkers in whole blood, providing additional options for rapid quantitative POCT tests