Abstract: Disclosed is a sub-Kelvin temperature zone refrigeration mechanism. The sub-Kelvin temperature zone refrigeration mechanism includes a pulse tube refrigeration unit, first pre-cooling heat exchangers, a throttling refrigeration unit, second pre-cooling heat exchangers, an adsorption refrigeration unit, a third pre-cooling heat exchanger and a dilution refrigeration unit. The pulse tube refrigeration unit includes a pulse tube refrigeration part. The throttling refrigeration unit includes a throttling refrigeration part, and the throttling refrigeration part is connected with the adsorption refrigeration unit through the second pre-cooling heat exchangers so as to pre-cool the adsorption refrigeration unit. The adsorption refrigeration unit includes an adsorption refrigeration part, and the adsorption refrigeration part is connected with the dilution refrigeration unit through the third pre-cooling heat exchanger.

Abstract: The present application relates to the technical field of further processing of dairy products, and in particular to a preparation method of milk oligosaccharides, and milk oligosaccharide powder and food prepared thereby. The preparation method comprises the steps of: performing ultrafiltration of whey liquid for at least three times, subjecting the ultrafiltration permeate to nanofiltration concentration for several times, then subjecting the nanofiltration retentate to chromatographic separation and purification, collecting chromatographic collection liquid containing sialyllactose while removing the fraction containing lactose, subjecting the collection to desalination and drying to obtain oligosaccharide powder. The milk oligosaccharides prepared by the present method and the food product containing the same comprise basically bovine milk oligosaccharides, which are light yellow or white in color, light in flavor, uniform in size, and have good thermal stability and solubility.

Abstract: The disclosed subject matter includes an active control alternating-direct flow hybrid mechanical cryogenic system, and relates to the field of cryogenic refrigeration technologies. The active control alternating-direct flow hybrid mechanical cryogenic system includes a main compressor, a Stirling cold finger, an intermediate heat exchanger, a pulse tube cold finger, a first dividing wall type heat exchanger, a final precooled heat exchanger, a second dividing wall type heat exchanger, and an evaporator that are communicated successively, where the second dividing wall type heat exchanger is connected to the evaporator through a second connecting pipeline, and a throttling element is disposed on the second connecting pipeline; a pulse tube cold head of the pulse tube cold finger is communicated with the final precooled heat exchanger through a cold chain; and a check valve is disposed on the intermediate heat exchanger.

Abstract: The disclosed subject matter includes an active control alternating-direct flow hybrid mechanical cryogenic system, and relates to the field of cryogenic refrigeration technologies. The active control alternating-direct flow hybrid mechanical cryogenic system includes a main compressor, a Stirling cold finger, an intermediate heat exchanger, a pulse tube cold finger, a first dividing wall type heat exchanger, a final precooled heat exchanger, a second dividing wall type heat exchanger, and an evaporator that are communicated successively, where the second dividing wall type heat exchanger is connected to the evaporator through a second connecting pipeline, and a throttling element is disposed on the second connecting pipeline; a pulse tube cold head of the pulse tube cold finger is communicated with the final precooled heat exchanger through a cold chain; and a check valve is disposed on the intermediate heat exchanger.