A method for the estimation of thermophysical properties of two-and multi-phase solid propellants is proposed in this paper.The theoretical solutions for thermal conductivity and specific heat of a homogeneous solid p...A method for the estimation of thermophysical properties of two-and multi-phase solid propellants is proposed in this paper.The theoretical solutions for thermal conductivity and specific heat of a homogeneous solid propellant cell in the transient thermal conductivity process are deduced on the condition that one boundary of the cell is heated while others are adiabatic.A homogenization theory and the finite element method are employed to compute the mean temperature and heat flux of a representative volume element(RVE).According to the mean results and the theoretical solutions,the effective thermal conductivity and specific heat of solid propellant can be estimated.A packing algorithm,considering the solid particles(ammonium perchlorate(AP)or aluminum)as spheres or discs,is used to match the size distribution and volume fraction of solid propellants,and some mesoscopic models of two-phase and three-phase solid propellants are established.According to the estimation theory proposed in this paper,the effective thermal conductivity and specific heat of solid propellants are predicted.The effect of AP or Al volume fraction is also discussed in this paper.展开更多
This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model c...This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.展开更多
Defensins play a vital role in the early stage of infection before adaptive immune responses are generated. Thus far, only limited detailed genomic data for avian defensin genes have been described. Here, using bacter...Defensins play a vital role in the early stage of infection before adaptive immune responses are generated. Thus far, only limited detailed genomic data for avian defensin genes have been described. Here, using bacterial ar- tificial chromosome libraries, we found that a 95 kb and 177 kb sequences in the golden pheasant （Chrysolophus pictus, Galliformes） and hwamei （Garrulax canorus, Passeriformes） corresponds to 16 and 30 defensin genes, respectively. Fluorescence in situ hybridization assigned defensin gene clusters in the golden pheasant and hwamei to chromosomes 2q and 3q, respectively. In combination with the previous chicken （Gallus gallus, Galliformes） and zebra finch （Taeniopygia guttata, Passeriformes） defensin clusters, the comparative genomic analysis revealed that lineage- specific duplications and deletions have given rise to clearly different genomic structures. On the basis of genomic char- acteristics, we further found that transposable elements act as agents of evolution, causing direct and indirect copy number variations in defensin genes via duplications. Tissue ex- pression analysis showed that the Passeriformes-specific duplicated AvBD1 and AvBD3 genes are mainly expressed in the upper and lower respiratory tract, tongue, and spleen. Our analyses indicate that the duplication-and-deletion of defensin genes conformed to the birth-and-death evolutionary process and that transposable elements induced theduplication of defensin genes. Moreover, the respiratory system-specific expression pattern of Passeriformes-specific expanded AvBD1 and AvBD3 genes suggests their important role in maintaining the singing trait of songbirds. The understanding of the genomic structure, expression, and evolution of defensin genes can provide a crucial immunological foundation to study and prevent avian diseases.展开更多
Background:Plateau zokor inhabits in sealed burrows from 2,000 to 4,200 meters at Qinghai-Tibet Plateau.This extreme living env ironment makes it a great model to study animal adaptation to hypoxia,low temperature,and...Background:Plateau zokor inhabits in sealed burrows from 2,000 to 4,200 meters at Qinghai-Tibet Plateau.This extreme living env ironment makes it a great model to study animal adaptation to hypoxia,low temperature,and high carbon dioxide concentration.Methods:We provide an integrated resource,ZokorDB,for tissue specific regulatory network annotation for zokor.ZokorDB is based on a high-quality draft genome of a plateau zokor at 3,300 m and its transcriptional profiles in brain,heart,liver,kidney,and lung.The conserved non-coding elements of zokor are annotated by their nearest genes and upstream transcriptional factor motif binding sites.Results:ZokorDB provides a general draft gene regulatory network(GRN),Le?potential transcription factor(TF)binds to non-coding regulatory elements and regulates the expression of target genes(TG).Furthermore,we refined the GRN by incorporating matched RNA-seq and DNase-seq data from mouse ENCODE project and reconstructed five tissue-specific regulatory networks.Conclusions:A web-based,open-access database is developed for easily searching,visualizing,and downloading the annotation and data.The pipeline of non-coding region annotation for zokor will be useful for other non-model species.ZokorDB is free available at the website(bigd.big.ac.cn/zokordb/).展开更多
文摘A method for the estimation of thermophysical properties of two-and multi-phase solid propellants is proposed in this paper.The theoretical solutions for thermal conductivity and specific heat of a homogeneous solid propellant cell in the transient thermal conductivity process are deduced on the condition that one boundary of the cell is heated while others are adiabatic.A homogenization theory and the finite element method are employed to compute the mean temperature and heat flux of a representative volume element(RVE).According to the mean results and the theoretical solutions,the effective thermal conductivity and specific heat of solid propellant can be estimated.A packing algorithm,considering the solid particles(ammonium perchlorate(AP)or aluminum)as spheres or discs,is used to match the size distribution and volume fraction of solid propellants,and some mesoscopic models of two-phase and three-phase solid propellants are established.According to the estimation theory proposed in this paper,the effective thermal conductivity and specific heat of solid propellants are predicted.The effect of AP or Al volume fraction is also discussed in this paper.
文摘This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.
基金supported by the National Natural Science Foundation of China(31070334)
文摘Defensins play a vital role in the early stage of infection before adaptive immune responses are generated. Thus far, only limited detailed genomic data for avian defensin genes have been described. Here, using bacterial ar- tificial chromosome libraries, we found that a 95 kb and 177 kb sequences in the golden pheasant （Chrysolophus pictus, Galliformes） and hwamei （Garrulax canorus, Passeriformes） corresponds to 16 and 30 defensin genes, respectively. Fluorescence in situ hybridization assigned defensin gene clusters in the golden pheasant and hwamei to chromosomes 2q and 3q, respectively. In combination with the previous chicken （Gallus gallus, Galliformes） and zebra finch （Taeniopygia guttata, Passeriformes） defensin clusters, the comparative genomic analysis revealed that lineage- specific duplications and deletions have given rise to clearly different genomic structures. On the basis of genomic char- acteristics, we further found that transposable elements act as agents of evolution, causing direct and indirect copy number variations in defensin genes via duplications. Tissue ex- pression analysis showed that the Passeriformes-specific duplicated AvBD1 and AvBD3 genes are mainly expressed in the upper and lower respiratory tract, tongue, and spleen. Our analyses indicate that the duplication-and-deletion of defensin genes conformed to the birth-and-death evolutionary process and that transposable elements induced theduplication of defensin genes. Moreover, the respiratory system-specific expression pattern of Passeriformes-specific expanded AvBD1 and AvBD3 genes suggests their important role in maintaining the singing trait of songbirds. The understanding of the genomic structure, expression, and evolution of defensin genes can provide a crucial immunological foundation to study and prevent avian diseases.
基金ZokorDB is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB13000000)The authors are also supported by the National Natural Science Foundation of China(NSFC)(Nos.11871463,11871462,61671444 and 61621003)+1 种基金We thank all the lab members for discussions on data collection,genome alignment,annotation,GRN reconstructionWe thank Dr.Yilei Wu and his group for help on database design and management.
文摘Background:Plateau zokor inhabits in sealed burrows from 2,000 to 4,200 meters at Qinghai-Tibet Plateau.This extreme living env ironment makes it a great model to study animal adaptation to hypoxia,low temperature,and high carbon dioxide concentration.Methods:We provide an integrated resource,ZokorDB,for tissue specific regulatory network annotation for zokor.ZokorDB is based on a high-quality draft genome of a plateau zokor at 3,300 m and its transcriptional profiles in brain,heart,liver,kidney,and lung.The conserved non-coding elements of zokor are annotated by their nearest genes and upstream transcriptional factor motif binding sites.Results:ZokorDB provides a general draft gene regulatory network(GRN),Le?potential transcription factor(TF)binds to non-coding regulatory elements and regulates the expression of target genes(TG).Furthermore,we refined the GRN by incorporating matched RNA-seq and DNase-seq data from mouse ENCODE project and reconstructed five tissue-specific regulatory networks.Conclusions:A web-based,open-access database is developed for easily searching,visualizing,and downloading the annotation and data.The pipeline of non-coding region annotation for zokor will be useful for other non-model species.ZokorDB is free available at the website(bigd.big.ac.cn/zokordb/).
