Fracture mechanism and separation conditions of pineapple fruit-stem and calibration of physical characteristic parameters

At present,the research on the physical composition and properties of pineapple plants is scarce,and the uncertainty of fruit picking method is the key bottleneck factor hindering the research and development of pineapple harvesting machinery.Based on the statistics of survey data from many places,this paper analyzes the fruit-stem fracture mechanism and the theoretical conditions for optimal separation through structural modeling,mechanical behavior analysis and function judgment.On this basis,the“pineapple plant fixation bench”and“fruit-stem bending separation torque test equipment”were developed,and large-size,small-size tests and random optimization tests were carried out successively.The test results showed that the larger of the stem-stalk fixation distance,the more torque and fracture starting angle required for fruit fracture would increase,and the change range was small when the stem-stalk fixation distance was within 50 mm,and the probability of brittle fracture and complete separation was very high.When the space between the fracture section and the fruit-stem connecting point is about 5mm,the range of bending moment value required for the fruit-stem fracture is 1.88 to 2.77 N·m,the range of fracture starting angle is 12.2°to 18.1°,and the angular travel range during the separation process is 82.9°to 87.5°.When the stem-stalk fixation distance is about 15 mm,it is the best fruit-stem separation condition and the breaking torque measured in the verification test is about 2.76 N·m.The fracture starting angle is about 13.8°,the maximum prediction error is 13.1%,and the elastic modulus near the fruit-stem joint ranges from 16.1 to 23.9 MPa.This conclusion can provide an important design basis for the research and development of pineapple field picking robot and harvesting equipment.

A Good GC Stationary Phase for Separation of Xylene Isomers

An excellent separation of xylene isomers is reported using 2, 6-O-di-pentyl-3-O-acetyl-beta-CD as capillary stationary phase. The optimum conditions for the separation are also discussed.

Approximate derivative-dependent functional variable separation for quasi-linear diffusion equations with a weak source

By using the approximate derivative-dependent functional variable separation approach, we study the quasi-linear diffusion equations with a weak source ut = （A（u）Ux）x ＋ eB（u, Ux）. A complete classification of these perturbed equations which admit approximate derivative-dependent functional separable solutions is listed. As a consequence, some approxi- mate solutions to the resulting perturbed equations are constructed via examples.

Effects of embedding direct reduction followed by magnetic separation on recovering titanium and iron of beach titanomagnetite concentrate

Embedding direct reduction followed by magnetic separation was conducted to fully recover iron and titanium separately from beach titanomagnetite （TTM）. The influences of reduction conditions, such as molar ratio of C to Fe, reduction time, and reduction temperature, were studied. The results showed that the TTM concentrate was reduced to iron and iron-titanium oxides, depending on the reduction time, and the reduction sequence at 1 200℃ was suggested as follows ： Fe2.75 Ti0.25O4→Fe2TiO4→FeTiO3→FeTi2O5. The reduction temperature played a considerable role in the reduction of TTM concentrates. Increasing temperature from 1 100 to 1 200℃ was beneficial to recovering titanium and iron, whereas the results deteriorated as temperature increased further. The results of X-ray diffraction and scanning electron microscopy analyses showed that low temperature （≤1100℃） was unfavorable for the gasification of reductant, resulting in insufficient reducing atmosphere in the reduction process. The molten phase was formed at high temperatures of 1250-1 300℃, which accelerated the migration rate of metallic particles and suppressed the diffusion of reduction gas, resulting in poor reduction. The optimum conditions for reducing TTM concentrate are as follows： molar ratio of C to Fe of 1.68, reduction time of 150 min, and reduction temperature of 1 200℃. Under these conditions, direct reduction iron powder, assaying 90.28 mass% TFe and 1.73 mass% TiO2 with iron recovery of 90.85%, and titanium concentrate, assaying 46.24 mass% TiO2 with TiO2 recovery of 91.15%, were obtained.