Concentration of α-Linoleic Acid of Perilla Oil by Gradient Cooling Urea Inclusion

In this study, production of ct-linoleic acid concentrated from crude perilla oil by gradient cooling urea inclusion was optimized. The fatty acid composition was determined after ethyl esterification by gas chromatography （GC）. In this process, orthogonal experiment was carried out. Under optimum conditions, the maximum amount of α-linoleic acid （91.5%） was obtained at a urea to fatty acid ratio of 3, a solvent to fatty acids ratio of 7, a reaction temperature of 348 K and a crystallization time of 690 min. A simple method of gradient cooling urea inclusion was used to purify α-linolenic acid by using urea to form inclusion complexes with the saturated and the less unsaturated fatty acids, which enhanced the purity of α-linoleic acid ethyl ester by above 90%.

Systematically investigating the polarization gradient cooling in an optical molasses of ultracold cesium atoms

We systematically investigate the polarization gradient cooling （PGC） process in an optical molasses of ultracold cesium atoms. The SR mode for changing the cooling laser, which means that the cooling laser frequency is stepped to the setting value while its intensity is ramped, is found to be the best for the PGC, compared with other modes studied. We verify that the heating effect of the cold atoms, which appears when the cooling laser intensity is lower than the saturation intensity, arises from insufficient polarization gradient cooling. Finally, an exponential decay function with a statistical explanation is introduced to explain the dependence of the cold atom temperature on the PGC interaction time.

Numerical simulation on gradient cooling behavior of jumbo slab ingot

Shrinkage porosity defect is often found in an air cooled jumbo steel ingot, which will influence the quality of the final rolled plates. In practical production, some rolled plates are frequently rejected due to the serious shrinkage porosity of the ingot. To improve the quality of the ingot, a new cooling method, gradient cooling process （in which the upper part of the ingot is air cooled and the lower part is spray cooled） was put forward in this study. The solidification behaviors for a 60 t jumbo slab ingot under gradient cooling condition were simulated using the ProCast software, and the results were compared with those of an ingot by air cooling condition. The solidifying tendency, temperature field and distribution of shrinkage porosities in the ingot under different cooling conditions were analyzed. Simulation results show that under gradient cooling condition the solidification of the slab ingot progresses in an upward manner along the vertical z axis and in a centripetal manner along the horizontal x and y axes. Gradient cooling can efficiently reduce shrinkage porosity of the jumbo slab ingot by optimizing the solidification sequence, and making the position of shrinkage porosity move from near the middle height of the ingot （under air cooling condition） towards the head of the ingot; and the secondary shrinkage is eliminated. In addition, the solidification time of the ingot under gradient cooling is 7.3 h in this simulation, which is 2.7 h faster than that under air cooling. A 60 t jumbo slab ingot was successfully produced under gradient cooling condition. The ingot was rolled to a plate with a thickness of 100 mm and length of 18,000 mm, and ultrasonic flaw detection was performed. Some porosity was found along the axis of the plate at 4,900 position of the defect is moved towards the head with the simulated result. - 6,000 mm from the head of the plate, indicating that the of the ingot. This distribution trend of the defect is consistent

A new preparation technology of structural- gradient materials without a brittle transition zone in a Mn-Si-Cr-B bainitic cast steel

In the present work, a unique gradient cooling heat treatment process(GCHT) for a Mn-Si-Cr-B bainitic cast steel was developed, and microstructure and mechanical properties were examined by OM, SEM, EBSD and a uniaxial tensile test. The results showed that the structural-gradient-material(SGM) with a gradient microstructure from granular bainite to martensite was successfully produced, and it exhibited a good ductility(~13.8%) at one end and an excellent ultimate strength(~1,720 MPa) at the other end. In between the bainite and martensite, a transition region with a superior combination of tensile strength and ductility(1,700 MPa and 11.1%) was obtained, which is different from the normal knowledge of a brittle transition region. Moreover, through changing the gradient of cooling rate, the optimized SGM with a new gradient microstructure from pearlite to martensite showed a more stable structural gradient and an improved ductility(22.8%) at one end. The microstructure variation in the sample was mainly related to the carbon diffusion rate during heat treatment, and the diffusion rate could be controlled by regulating the cooling velocity. Therefore, the SGMs with different gradient microstructures could be designed to meet the needs of different properties. As a result, this work provides a new approach for preparation of the gradient structured steel, which has potential for practical application for dual-property automobile parts.