The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are propose...The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid muhi-block systems.The stiff- ness proportional damping is constructed for the prescribed damping ratio,based on the non-zero fundamental frequency ef- fective during the time interval while the boundary conditions remain essentially constant.At this time interval,the funda- mental frequency can be estimated without complete eigenvalue analysis.The damping coefficients will vary while the damp- ing ratio remains the same throughout the entire analysis.A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases.These procedures were implemented in the development of the dis- tinet element method for the dynamic analyses of piled multi-block systems.The analysis results |or the single-block and two-block systems were in a good agreement with the analytic predictions.Applications to the seismic analyses of piled four- block systems revealed that the new procedures can make a significant difference and may lead to much-improved results.展开更多
Different tougheners including methyl methacrylate-butadiene-styrene terpolymer (MBS, core-shell type), maleic anhydride (MAH) grafted ethylene-octene copolymer (EOM), and MAH grafted polyethylene wax (PEM) were inves...Different tougheners including methyl methacrylate-butadiene-styrene terpolymer (MBS, core-shell type), maleic anhydride (MAH) grafted ethylene-octene copolymer (EOM), and MAH grafted polyethylene wax (PEM) were investigated for toughening the polycarbonate (PC) composites reinforced by short carbon fiber (SCF) and flake graphene (FG). The effects of tougheners on the preparation, thermal conductivity and mechanical properties of PC composites were studied. Scanning electron microscopy was used for characterizing the impact fracture surfaces of the composites. The results showed that introducing tougheners into the carbon reinforced PC composites was beneficial to improving the processability, and PEM was more effective than EOM and MBS. Meanwhile, the through-thickness and the in-plan thermal conductivity decreased to some degree due to the isolated island effects of tougheners. Moreover, the brittle PC composites with high flexural stress could be easily toughened by tougheners. In contrast, PEM had better toughening function than EOM and MBS, and correspondingly, the stiffness of the composites was the lowest for the PEM toughened systems. The fractography revealed that dense and uniformly distributed carbon fillers dispersed in matrix PC and circular cavities coexisted in the composites. The naked fiber length gradually increased as the ductility of composite materials improved.展开更多
In this paper, we proposed 10 Gb/s transmission using 4-channel polymer waveguides on the optical electronic printed circuit board. It was simulated by the ray tracing method for tolerance study of optical interconnec...In this paper, we proposed 10 Gb/s transmission using 4-channel polymer waveguides on the optical electronic printed circuit board. It was simulated by the ray tracing method for tolerance study of optical interconnection and fabrication. In order for easy fabrication and high position accuracy, the polymer waveguides were forming silver coated 45° reflective mirrors by dicing method and e-beam deposition for 90° light beam turning. The coupling loss was demonstrated in different polishing grit sizes. The optical interconnection in board-embed 4-channel flexible waveguides was demonstrated with a low propagation loss of 0.1 dB/cm and a clear eye diagram at 2.5 Gb/s data rate per channel.展开更多
Tuberculosis (TB) is one of the major causes of morbidity and mortality worldwide. In India, nearly 1.8 million new cases of TB are reported annually, which accounts for a fifth of new cases in the world—greater than...Tuberculosis (TB) is one of the major causes of morbidity and mortality worldwide. In India, nearly 1.8 million new cases of TB are reported annually, which accounts for a fifth of new cases in the world—greater than in any other country. Anti-tubercular drugs (ATDs) have been used for decades, and widespread resistance to them is a very serious public health concern in any part of the world. Aim of this study was to determine the prevalence of Rifampicin (the first line Anti-TB drug) resistance among both pulmonary and extra-pulmonary samples tested positive for Mycobacterium tuberculosis and thereby predict the prevalence of Multi-drug resistant (MDR) tuberculosis in Kolkata and its Suburban regions. All 331 randomly collected clinical samples (both Pulmonary and Extra Pulmonary) were initially screened by Zeihl-Neelsen AFB staining followed by culture on BacT/Alert 3D system and on Lowenstein-Jensen medium and the positive samples were subjected to detection of Mycobacterium tuberculosis complex (MTBC) and simultaneous analysis of Rifampicin resistance by Xpert MTB/RIF assay. Out of the 51 (15.40%) culture positive samples, 13.7% of pulmonary samples and 9.09% of extra-pulmonary samples were Rifampicin resistant. The prevalence of Rifampicin resistant TB in our study is high and the possible reasons can be mixing of new as well as retreatment cases and smaller sample size but, yet it can help Government and public health regulatory bodies to formulate adequate strategies to fight against drug resistant tuberculosis, especially in this part of the world.展开更多
文摘The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid muhi-block systems.The stiff- ness proportional damping is constructed for the prescribed damping ratio,based on the non-zero fundamental frequency ef- fective during the time interval while the boundary conditions remain essentially constant.At this time interval,the funda- mental frequency can be estimated without complete eigenvalue analysis.The damping coefficients will vary while the damp- ing ratio remains the same throughout the entire analysis.A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases.These procedures were implemented in the development of the dis- tinet element method for the dynamic analyses of piled multi-block systems.The analysis results |or the single-block and two-block systems were in a good agreement with the analytic predictions.Applications to the seismic analyses of piled four- block systems revealed that the new procedures can make a significant difference and may lead to much-improved results.
文摘Different tougheners including methyl methacrylate-butadiene-styrene terpolymer (MBS, core-shell type), maleic anhydride (MAH) grafted ethylene-octene copolymer (EOM), and MAH grafted polyethylene wax (PEM) were investigated for toughening the polycarbonate (PC) composites reinforced by short carbon fiber (SCF) and flake graphene (FG). The effects of tougheners on the preparation, thermal conductivity and mechanical properties of PC composites were studied. Scanning electron microscopy was used for characterizing the impact fracture surfaces of the composites. The results showed that introducing tougheners into the carbon reinforced PC composites was beneficial to improving the processability, and PEM was more effective than EOM and MBS. Meanwhile, the through-thickness and the in-plan thermal conductivity decreased to some degree due to the isolated island effects of tougheners. Moreover, the brittle PC composites with high flexural stress could be easily toughened by tougheners. In contrast, PEM had better toughening function than EOM and MBS, and correspondingly, the stiffness of the composites was the lowest for the PEM toughened systems. The fractography revealed that dense and uniformly distributed carbon fillers dispersed in matrix PC and circular cavities coexisted in the composites. The naked fiber length gradually increased as the ductility of composite materials improved.
文摘In this paper, we proposed 10 Gb/s transmission using 4-channel polymer waveguides on the optical electronic printed circuit board. It was simulated by the ray tracing method for tolerance study of optical interconnection and fabrication. In order for easy fabrication and high position accuracy, the polymer waveguides were forming silver coated 45° reflective mirrors by dicing method and e-beam deposition for 90° light beam turning. The coupling loss was demonstrated in different polishing grit sizes. The optical interconnection in board-embed 4-channel flexible waveguides was demonstrated with a low propagation loss of 0.1 dB/cm and a clear eye diagram at 2.5 Gb/s data rate per channel.
文摘Tuberculosis (TB) is one of the major causes of morbidity and mortality worldwide. In India, nearly 1.8 million new cases of TB are reported annually, which accounts for a fifth of new cases in the world—greater than in any other country. Anti-tubercular drugs (ATDs) have been used for decades, and widespread resistance to them is a very serious public health concern in any part of the world. Aim of this study was to determine the prevalence of Rifampicin (the first line Anti-TB drug) resistance among both pulmonary and extra-pulmonary samples tested positive for Mycobacterium tuberculosis and thereby predict the prevalence of Multi-drug resistant (MDR) tuberculosis in Kolkata and its Suburban regions. All 331 randomly collected clinical samples (both Pulmonary and Extra Pulmonary) were initially screened by Zeihl-Neelsen AFB staining followed by culture on BacT/Alert 3D system and on Lowenstein-Jensen medium and the positive samples were subjected to detection of Mycobacterium tuberculosis complex (MTBC) and simultaneous analysis of Rifampicin resistance by Xpert MTB/RIF assay. Out of the 51 (15.40%) culture positive samples, 13.7% of pulmonary samples and 9.09% of extra-pulmonary samples were Rifampicin resistant. The prevalence of Rifampicin resistant TB in our study is high and the possible reasons can be mixing of new as well as retreatment cases and smaller sample size but, yet it can help Government and public health regulatory bodies to formulate adequate strategies to fight against drug resistant tuberculosis, especially in this part of the world.
