Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrest...Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.展开更多
The stability of a river-bed protection block in a flood event is affected by underscouring of the block. The effects of block spacing on block stability were investigated in different underscour conditions. Three blo...The stability of a river-bed protection block in a flood event is affected by underscouring of the block. The effects of block spacing on block stability were investigated in different underscour conditions. Three blocks were placed at the bottom in a flume, and the underscour depth of the frontal block and distance between the first and second blocks were changed. Drag and lift forces were measured directly in each experimental condition. Particle Image Velocimetry (PIV) was used to visualize the flow and eva- luate the streamline pattern. Pressure measurements around the block to understand the pressure distribution show that the pressure distribution on the rear and bottom surfaces of the block is significantly affected by changes in block spacing and underscour depth. The experimental results show that for the same underscour gap, lift, and drag coefficients decreased with increasing space between the two blocks. In addition, if the underscour gap is increased with the same horizontal spacing, the lift coefficient increases and drag coefficient decreases. These results demonstrate that wider spacing enhance stability of the frontal block in the underscour condition. Moreover, analysis of block stability with changing underscouring and horizontal spacing shows that bed protection blocks seem to have more stability when the gap between two bed protection blocks was equal to height of the blocks.展开更多
This paper proposes the critical conditions for a submerged ice block beneath an intact ice cover to become unstable,as a fundamental component of any numerical model to successfully predict the ice jam formation or t...This paper proposes the critical conditions for a submerged ice block beneath an intact ice cover to become unstable,as a fundamental component of any numerical model to successfully predict the ice jam formation or the ice jam release events.The flume model experimental and numerical simulation methods are both applied to analyze the stability of submerged ice blocks.The flume model experiment is first conducted,and the experimental results indicate that the influencing factors of the stability of a submerged ice block include the relative length,the relative water depth and the relative width.It was shown that the effect of the relative width on the stability of submerged ice blocks was not well studied.Based on the experimental results,the k-eturbulence model is applied to establish a 3-D numerical model for studying the pressure distribution beneath submerged ice blocks.The effects of the relative width on the Venturi pressure and the leading edge pressure are evaluated.Finally,according to the force balance equation and the moment balance equation,this paper proposes a computational formula for the sliding and underturning critical conditions of submerged ice blocks,and the results are in good agreement with the experimental results.展开更多
Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide)(endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bi...Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide)(endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide)(exo-PTNP-b-exo-PCONBI) were synthesized by ring-opening metathesis polymerization. The endo- or exoPTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNPb-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant(?) of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low ? of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photocrosslinking, the polymer film has an increased ? of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ?C, and an enhanced decomposition temperature of 405 ?C, compared to those of polymer films without irradiation.展开更多
The solid form of drugs plays a central role in optimizing the physicochemical properties of drugs,and new solid forms will provide more options to achieve the desirable pharmaceutical profiles of drugs.Recently,certa...The solid form of drugs plays a central role in optimizing the physicochemical properties of drugs,and new solid forms will provide more options to achieve the desirable pharmaceutical profiles of drugs.Recently,certain drugs have been found to form crystalline inclusion complexes(ICs) with multiple types of linear polymers,representing a new subcategory of pharmaceutical solids.In this study,we used diflunisal(DIF) as the model drug host and extended the guest of drug/polymer ICs from homopolymers to block copolymers of poly(ethylene glycol)(PEG) and poly(s-caprolactone)(PCL).The block length in the guest copolymers showed a significant influence on the formation,thermal stability and dissolution behavior of the DIF ICs.Though the PEG block could hardly be included alone,it could indeed be included in the DIF ICs when the PCL block was long enough.The increase of the PCL block length produced IC crystals with improved thermal stability.The dissolution profiles of DIF/block copolymer ICs exhibited gradually decreased aqueous solubility and dissolution rate with the increasing PCL block length.These results demonstrate the possibility of using drug/polymer ICs to modulate the desired pharmaceutical profiles of drugs in a predictable and controllable manner.展开更多
The solid forms of drugs play a central role in controlling their physicochemical properties and consequently the bioavailability. Multiple types of drug solid forms have been developed to achieve the desirable pharma...The solid forms of drugs play a central role in controlling their physicochemical properties and consequently the bioavailability. Multiple types of drug solid forms have been developed to achieve the desirable pharmaceutical profiles, but new solid forms will provide more options for the solid-state property optimization and hence are highly desirable. This review focuses on a new pharmaceutical solid form, drug-polymer inclusion complexes (ICs), and summarizes their structural features, structure- property relationships, as well as potential pharmaceutical applications展开更多
基金support of the National Natural Science Foundation of China(Grant No.42102316)the Open Project of the Technology Innovation Center for Geological Environment Monitoring of Ministry of Natural Resources of China(Grant No.2022KFK1212005).
文摘Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.
基金the Maeda Engineering Foundation and Kyoritsu International Foundation for their financial support
文摘The stability of a river-bed protection block in a flood event is affected by underscouring of the block. The effects of block spacing on block stability were investigated in different underscour conditions. Three blocks were placed at the bottom in a flume, and the underscour depth of the frontal block and distance between the first and second blocks were changed. Drag and lift forces were measured directly in each experimental condition. Particle Image Velocimetry (PIV) was used to visualize the flow and eva- luate the streamline pattern. Pressure measurements around the block to understand the pressure distribution show that the pressure distribution on the rear and bottom surfaces of the block is significantly affected by changes in block spacing and underscour depth. The experimental results show that for the same underscour gap, lift, and drag coefficients decreased with increasing space between the two blocks. In addition, if the underscour gap is increased with the same horizontal spacing, the lift coefficient increases and drag coefficient decreases. These results demonstrate that wider spacing enhance stability of the frontal block in the underscour condition. Moreover, analysis of block stability with changing underscouring and horizontal spacing shows that bed protection blocks seem to have more stability when the gap between two bed protection blocks was equal to height of the blocks.
基金supported by the Funds for Creative Research Groups of China(Grant No.51321065)the Tianjin Municipal Science and Technology Project(Grant No.13JCZDJC35100)
文摘This paper proposes the critical conditions for a submerged ice block beneath an intact ice cover to become unstable,as a fundamental component of any numerical model to successfully predict the ice jam formation or the ice jam release events.The flume model experimental and numerical simulation methods are both applied to analyze the stability of submerged ice blocks.The flume model experiment is first conducted,and the experimental results indicate that the influencing factors of the stability of a submerged ice block include the relative length,the relative water depth and the relative width.It was shown that the effect of the relative width on the stability of submerged ice blocks was not well studied.Based on the experimental results,the k-eturbulence model is applied to establish a 3-D numerical model for studying the pressure distribution beneath submerged ice blocks.The effects of the relative width on the Venturi pressure and the leading edge pressure are evaluated.Finally,according to the force balance equation and the moment balance equation,this paper proposes a computational formula for the sliding and underturning critical conditions of submerged ice blocks,and the results are in good agreement with the experimental results.
基金financially supported by the National Natural Science Foundation of China(Nos.21574041 and 21374030)Large Instruments Open Foundation of East China Normal University(No.20151006)
文摘Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide)(endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide)(exo-PTNP-b-exo-PCONBI) were synthesized by ring-opening metathesis polymerization. The endo- or exoPTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNPb-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant(?) of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low ? of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photocrosslinking, the polymer film has an increased ? of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ?C, and an enhanced decomposition temperature of 405 ?C, compared to those of polymer films without irradiation.
基金financially supported by the National Natural Science Foundation of China(Nos.21434008,21374054)National Basic Research Program of China(973 Program,No.2014CB932202)
文摘The solid form of drugs plays a central role in optimizing the physicochemical properties of drugs,and new solid forms will provide more options to achieve the desirable pharmaceutical profiles of drugs.Recently,certain drugs have been found to form crystalline inclusion complexes(ICs) with multiple types of linear polymers,representing a new subcategory of pharmaceutical solids.In this study,we used diflunisal(DIF) as the model drug host and extended the guest of drug/polymer ICs from homopolymers to block copolymers of poly(ethylene glycol)(PEG) and poly(s-caprolactone)(PCL).The block length in the guest copolymers showed a significant influence on the formation,thermal stability and dissolution behavior of the DIF ICs.Though the PEG block could hardly be included alone,it could indeed be included in the DIF ICs when the PCL block was long enough.The increase of the PCL block length produced IC crystals with improved thermal stability.The dissolution profiles of DIF/block copolymer ICs exhibited gradually decreased aqueous solubility and dissolution rate with the increasing PCL block length.These results demonstrate the possibility of using drug/polymer ICs to modulate the desired pharmaceutical profiles of drugs in a predictable and controllable manner.
基金supported by the National Natural Science Foundation of China (No. 21434008)
文摘The solid forms of drugs play a central role in controlling their physicochemical properties and consequently the bioavailability. Multiple types of drug solid forms have been developed to achieve the desirable pharmaceutical profiles, but new solid forms will provide more options for the solid-state property optimization and hence are highly desirable. This review focuses on a new pharmaceutical solid form, drug-polymer inclusion complexes (ICs), and summarizes their structural features, structure- property relationships, as well as potential pharmaceutical applications