Abstract: A preforming method for a high-strength steel variable-diameter tubular part is provided, which belongs to the technical field of metal forming process. The preforming method for a high-strength steel variable-diameter tubular part includes: selecting a tubular blank; and preparing a tubular blank forming mold, where the tubular blank forming mold includes a preforming mold and a final forming mold; sealing and pressurizing the tubular blank; heating the tubular blank by using electrodes; preforming the tubular part at a constant temperature; maintaining a temperature Tl and moving the preformed tubular part to the final forming mold; finally forming the tubular part. Through two steps of operation of preforming and final forming, and maintaining a temperature during moving the tubular blank between the two steps, so that the conversion of intrametallic structure between the two steps is improved, and the performance of the tubular part is improved.

Abstract: A polynucleotide having promoter activity of a malate dehydrogenase gene (mdh gene), a transcription expression cassette, recombinant expression vector and recombinant host cell containing the polynucleotide having the promoter activity, a method for constructing a promoter mutant, a method for regulating the transcription of a target gene, a method for preparing a protein, and method for producing a target compound. The polynucleotide having the promoter activity is a mutant of an mdh gene promoter, and compared with a promoter of a wild-type mdh gene, the promoter activity of the mutant is significantly improved. After operably linking the mutant to a target gene, the expression efficiency of the target gene can be significantly improved, thereby effectively improving the yield and transformation rate of a target compound.

Abstract: A protein having an L-proline efflux function and the use thereof are provided. A method for producing L-proline or hydroxyproline by means of using a protein ThrE is used for producing L-proline by means of enhancing the activity of a polypeptide, having an L-proline efflux function, in an L-proline-producing strain. Alternatively, the method is used for producing hydroxyproline by means of weakening the activity of a polypeptide, having an L-proline efflux function, in L-proline-producing host cells and enhancing the activity of a proline hydroxylase.

Abstract: The present application relates to a composite binding agent grinding wheel, wherein a weight percentage of each raw material of the grinding wheel is: 45-65% of pretreatment abrasive, 8-20% of resin bonding agent, 5-12% of hexagonal boron nitride, 5-10% of silicon dioxide, 5-15% of ceramic powder, 6-12% of prealloy powder bonding agent, and 1-3% of boron powder. The composite binding agent super-hard grinding wheel prepared by the present application can achieve nano-level grinding surface quality when grinding epitaxial wafers, and the grinding wheel has strong self-sharpening and high sharpness. It has obvious advantages in the finishing of silicon carbide crystal epitaxial wafers, which can solve the current limitations of back thinning processing of silicon carbide crystal epitaxial wafers.

Abstract: The present application relates to a composite binding agent grinding wheel, wherein a weight percentage of each raw material of the grinding wheel is: 45-65% of pretreatment abrasive, 8-20% of resin bonding agent, 5-12% of hexagonal boron nitride, 5-10% of silicon dioxide, 5-15% of ceramic powder, 6-12% of prealloy powder bonding agent, and 1-3% of boron powder. The composite binding agent super-hard grinding wheel prepared by the present application can achieve nano-level grinding surface quality when grinding epitaxial wafers, and the grinding wheel has strong self-sharpening and high sharpness. It has obvious advantages in the finishing of silicon carbide crystal epitaxial wafers, which can solve the current limitations of back thinning processing of silicon carbide crystal epitaxial wafers.