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To study the application of a machine learning algorithm for predicting gestational diabetes mellitus (GDM) in early pregnancy.

Experiments and computational fluid dynamics (CFD) simulation were used to analyze the effects of the number and the diameter of oxygen supply ports, the flow rate and the mode of oxygen supply, and different modes of air flow (up-inlet and down-outlet on the same side, or on the different side) on the indoor oxygen enrichment characteristics and the effect of anoxic conditions in a closed buildings with or without air conditioning. Without air conditioning, the number and the diameter of oxygen supply ports, the flow rate and mode of oxygen supply, and formed oxygen-enriched regions are quite different. Using a double-45°-opposite oxygen supply ports with a diameter of 6 mm is advisable. Under the air conditioning condition, the number and the diameter of oxygen supply ports, the flow rate of oxygen supply, and the modes of air flow are different too. The formed oxygen-enriched area are all generally elliptical. It is advisable to use a single oxygen supply port with a diameter of 6 mm and an air flow mode of up-inlet and down-outlet on the different side. When the flow rate of the oxygen supply is the same, the oxygen-enriched area are formed by the wind speed of 0.85 m·s-1 is approximately 20% larger than that formed by the 1 m·s-1 wind speed. When the air supply wind speed is 0.85 m·s-1 and the oxygen supply flow rate is 1.5 m3·h-1, the oxygen-enriched area is approximately 0.96 m2, which is consistent with the area of the single-person activity. It is suitable as the basic oxygen-enriched supply for the single-person under air conditioning conditions where are lack of oxygen.

A set of experimental devices for the measurement of indoor oxygen supply in an enclosed architectural space was built. The devices were used to analyze the effects of the number and diameter of oxygen-feeding ports, oxygen flow rate, and oxygen-feeding mode on the indoor oxygen enrichment characteristics and efficiency of an architectural space. Results show that the distribution of the maximum axial oxygen concentration tends to decline with axial distance under different numbers and diameters of oxygen-feeding ports, oxygen flow rates, and oxygen-feeding modes. Axial oxygen concentration rapidly decreases when the axial distance to the oxygen-feeding port ranges from 0 m to 0.55. In general, the oxygen-enriched region that forms in a single oxygen-feeding port under different pipe diameters and oxygen flow rates presents a flat elliptical shape. The oxygen-enriched area expands under a constant oxygen-feeding pipe diameter and an increasing oxygen flow rate. The oxygen-enriched area that forms in double oxygen-feeding ports, wherein one is positioned vertically forward and the other port is positioned 45° opposite the forward-facing port, has a bifurcated shape with one pointed head and one rounded head. The oxygen-enriched area that forms in the vertical forward-facing port is larger than that in the 45° opposing port. Under back-to-back oxygen feeding, the oxygen-enriched area that forms in double oxygen-feeding ports with the pipe diameter of 6 mm generally exhibits a two-bladed fan shape, whereas that in double oxygen-feeding ports with the pipe diameter of 10 mm appears as two overlapping semicircles. Under the total oxygen delivery flow rate of 1 m3·h-1, the range of oxygen feeding in double oxygen-feeding ports with the pipe diameter of 6 mm and 45° angle is the largest and that in double oxygen-feeding ports with the pipe diameter of 10 mm and vertical forward position is the smallest. Under a constant total oxygen flow rate and oxygen-feeding mode, the oxygen-enriched area that forms in the single oxygen-feeding port in the vertical forward position is 20% larger than that in the double oxygen-feeding ports in the vertical forward position. Under the same number of oxygen-feeding port, oxygen flow rate, and oxygen-feeding mode, the oxygen-enriched area in the oxygen-feeding port with the pipe diameter of 6 mm is approximately 60% larger than that in the oxygen-feeding port with the pipe diameter of 10 mm.

The internal flow characteristics of axial flow absorbers were numerically studied by the computational fluid dynamics(CFD) method. The influences of three absorber models on the internal flow uniformity were compared: absorber without a flow distributor,absorber with a single flow distributor,and absorber with the combination of a flow distributor and a baffle. The results show that the flow is severely uneven without a flow distributor,is slightly meliorated with a single flow distributor,and is significantly improved with the combination of a flow distributor and a baffle. For the combined configuration,the best flow uniformities are obtained with the pore diameter of 0.003 m as the pore opening ratio remains unchanged and with the pore opening ratio of 0.388 as the pore diameter does not change.

The microstructure of as-cast GH625 alloy was investigated on the basis of experimental methods such as Thermo-Calc software,scanning electron microscopy and energy dispersive spectroscopy. The effect of casting temperature on the microstructure was also analyzed by comparing different samples. The microstructure of as-cast GH625 alloy is a dendritic structure and M6C carbides accompanied with δ phase precipitate in the interdendritic area. Both primary dendrite arm spacing(λ1) and second dendrite arm spacing(λ2) increase with the increase of casting temperature; however,the microsegregation is affected by both diffusion distance and diffusion time. The comprehensive interaction of these two factors leads to the greatest microsegregation degree of Nb at 1420℃,which contributes to δ phase precipitation in the interdendritic area. As a result,diffusion distance and diffusion time should be comprehensively considered in making the casting process,so as to choose a proper casting temperature(or cooling rate).

A radial flow pressure swing adsorption (PSA) unit with two-tower configuration was designed for oxygen production. The influences of gas flow pattern, outer flow channel width and channel structure on oxygen production were studied by experiment. The result indicates that it is an optimal choice to use centripetal flow in the radial flow adsorber for oxygen production with PSA. Un-der the experimental condition, when the outer flow channel width decreases to 13 mm, the separation of oxygen from nitrogen is the best. A R-shaped channel structure can better improve the utilization efficiency of molecular sieves and oxygen production compared with a Z-shaped channel. This research result provides a foundation for the application and research of a radial flow adsorber in the PSA unit for oxygen production.

Uniform gas distribution in a radial flow adsorber plays an essential part in its performance. A 3D hydrodynamic and mathematical model of the radial flow adsorber was developed based on experimental studies. The effects of flow patterns, the cross-section ratio of central channel to outer channel, and the opening ratios of the central channel and the outer channel were comparatively studied by using this model. Radial inward flow was proved to have a better performance than radial outward flow, and the∏ type of inward flow is a little better than that of the Z type of inward flow. The best effect can be obtained when the cross-section ratio of central channel to outer channel is 18.9%. The radial non-uniformity of velocity decreases with the decrease of the opening ratio of the central channel, and the effect of flow distribution is better. But if the opening ratio of the central channel is too low, it will cause uneven local flow distribution and high energy consumption. The opening ratio of the outer channel has a little influence on flow distribution in the radial flow adsorber.