Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanica...Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanical properties due to its composition, structure and sedimentary environment. In this contribution, we discuss its specific gravity, porosity ratio compressibility, crushing, shearing and intensity for coral sand samples from the Nansha islands based on laboratory mechanical tests. Our results show distinct high porosity ratio, high friction angle and low intensity as compared with the quartz sand. We believe that grain crushing is the main factor that influences the deformation and strength of coral sand. Comprehensive study on the physical and mechanical properties of coral sands is significant in providing reliable scientific parameters to construction on coral islet, and thus avoids accidents in construction.展开更多
The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model(DBM) has the potential to investigate flo...The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model(DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation.It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model.Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model.To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified.展开更多
Let D be an integral domain, ＊a star-operation on D, and S a multiplicative subset of D. We define D to be an S-＊w-principal ideal domain if for each nonzero ideal I of D, there exist an element s ∈ S and a princip...Let D be an integral domain, ＊a star-operation on D, and S a multiplicative subset of D. We define D to be an S-＊w-principal ideal domain if for each nonzero ideal I of D, there exist an element s ∈ S and a principal ideal （c） of D such that sI （c） In this paper, we study some properties of S-＊w-principal ideal domains. Among other things, we study the local property, the Nagata type theorem, and the Cohen type theorem for S-＊w-principal ideal domains.展开更多
文摘Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanical properties due to its composition, structure and sedimentary environment. In this contribution, we discuss its specific gravity, porosity ratio compressibility, crushing, shearing and intensity for coral sand samples from the Nansha islands based on laboratory mechanical tests. Our results show distinct high porosity ratio, high friction angle and low intensity as compared with the quartz sand. We believe that grain crushing is the main factor that influences the deformation and strength of coral sand. Comprehensive study on the physical and mechanical properties of coral sands is significant in providing reliable scientific parameters to construction on coral islet, and thus avoids accidents in construction.
基金Support of National Natural Science Foundation of China under Grant Nos.11475028,11772064,and 11502117Science Challenge Project under Grant Nos.JCKY2016212A501 and TZ2016002
文摘The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model(DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation.It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model.Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model.To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified.
文摘Let D be an integral domain, ＊a star-operation on D, and S a multiplicative subset of D. We define D to be an S-＊w-principal ideal domain if for each nonzero ideal I of D, there exist an element s ∈ S and a principal ideal （c） of D such that sI （c） In this paper, we study some properties of S-＊w-principal ideal domains. Among other things, we study the local property, the Nagata type theorem, and the Cohen type theorem for S-＊w-principal ideal domains.
