Ultrasound promotes germination of aging Pinus tabuliformis seeds is associated with altered lipid metabolism.

Seed germination is an essential biological process for establishing new organisms of higher plants, it is especially significant for those aged seeds stored in gene banks for years. In this study, we investigated ultrasound treatment induced germination for aged Pinus tabuliformis seeds, which has been used in large scale aircraft sowing based afforestation in North China over 30 years' ago without knowing possible mechanisms. We showed certain strength of ultrasound could increase the germination rate of aged seeds for about 3 times compare with control.

A Quantitative Study of Micro and Macro Mechanical Parameters Based on the PFC Flat-Joint Model.

The flat-joint model, which constructs round particles as polygons, can suppress rotation after breakage between particles and simulate more larger compression and tension ratios than the linear parallel-bond model. The flat-joint contact model was chosen for this study to calibrate the rock for 3D experiments. In the unit experiments, the triaxial unit was loaded with flexible boundaries, and the influence of each microscopic parameter on the significance magnitude of the macroscopic parameters (modulus of elasticity , Poisson's ratio , uniaxial compressive strength , crack initiation strength , internal friction angle and uniaxial tensile strength ) was analysed by ANOVA (Analysis of Variance) in an orthogonal experimental design.

Damage Evolution Constitutive Behavior of Rock in Thermo-Mechanical Coupling Processes.

For thermal and loaded rock in engineering structures for some projects, triple-shear Drucker-Prager yield criteria, compaction coefficient , damage variable correction factor , and thermal damage variable are introduced in a new thermomechanical (TM) constitutive model for the entire process. The compaction stage of rock in uniaxial compression test and the strain softening of rock caused by thermal attack are considered in this article. The damage evolution of rocks is described by a damage variable and a constitutive equation, which are in agreement with the actual thermal experimental breakage.

Investigation of Microcrack Propagation and Energy Evolution in Brittle Rocks Based on the Voronoi Model.

The cracking of rock mass under compression is the main factor causing structural failure. Therefore, it is very crucial to establish a rock damage evolution model to investigate the crack development process and reveal the failure and instability mechanism of rock under load. In this study, four different strength types of rock samples from hard to weak were selected, and the Voronoi method was used to perform and analyze uniaxial compression tests and the fracture process.