Abstract: A tracer diffusion device includes: a first container, for holding a first fluid containing a tracer; a second container, for holding a second fluid; a drilling pipe; wherein, a first end of the drilling pipe is connected to the first container; a second end of the drilling pipe is extended into a borehole; and the second end of the drilling pipe is equipped with a first sealing capsule and a second sealing capsule; a plurality of through holes are arranged on the drilling pipe between the first sealing capsule and the second sealing capsule; a unidirectional driving device, arranged on the drilling pipe, for injecting the first fluid from the first container into the borehole between the first sealing capsule and the second sealing capsule; and a bidirectional driving device, arranged between the second container and the first sealing capsule.

Abstract: A polylactic acid triblock copolymer and a preparation method thereof are described. The polylactic acid triblock copolymer comprises an aromatic polyester oligomer block and a polylactic acid block. The polylactic acid triblock copolymer is obtained by reacting an aromatic polyester oligomer with a monomer lactide at a desired temperature. The polylactic acid block copolymer has a regular structure indicated by peak melting temperatures (Tm) corresponding to the aromatic polyester oligomer block and the polylactic acid block, respectively. Examples of the aromatic polyester oligomer block include polyethylene terephthalate, polybutylene terephthalate, and polyethylene 1,4-naphthalate. Examples of the monomer lactide include L-lactide and D-lactide.

Abstract: Disclosed are a polylactic acid block copolymer and a preparation method thereof. The polylactic acid block copolymer comprises block A and block B, and is presented as B-b-A-b-B triblock structure, wherein the block A is a cyclic aromatic polyester oligomer block, and the block B is a polylactic acid block. The polylactic acid block copolymer is obtained by ring-opening copolymerization of a cyclic aromatic polyester oligomer and a lactide. Disclosed are another polylactic acid block copolymer and a preparation method thereof. The polylactic acid block copolymer comprises block A and block B, and is presented as B-b-A-b-B triblock structure, wherein the block A is an aromatic polyester block with two hydroxyl end groups, and the block B is a polylactic acid block. The polylactic acid block copolymer is obtained by ring-opening copolymerization of an aromatic polyester with two hydroxyl end groups and a lactide.