From the view of energy state of material, this paper introduces a concept of weathering potential in carrying out quantitative calculation of the relevant products at different stages of rock-weathering and primary s...From the view of energy state of material, this paper introduces a concept of weathering potential in carrying out quantitative calculation of the relevant products at different stages of rock-weathering and primary soil-forming processes, elaborates respectively on weathering degree in the bio-weathering layer of rocks and during the formation of soil material and clay, and evaluats the further tendency of weathering in the above-mentioned stages. The authors have discovered that the scales of weathering potential of the materials increase successively in the three stages, which indicates that the products in the above-mentioned three stages must have undergone stronger and stronger weathering in the primitive forming process of soil in Fildes Peninsula, Antarctic. But, because of relatively weak chemical weathering, it is reasonable that there are much more skeleton grains and little clay in primary soils in this region. Meanwhile, the authors have also verified that the weathering potential of crude rock determines to some extent decrease in the products' weathering potential in the different stages in primary soil-forming, thereby plays an important role in the genesis and development of the primary soil in the studied area.展开更多
Airframe structural optimization at different design stages results in new mass and stiffness distributions which modify the critical design loads envelop. Determination of aircraft critical loads is an extensive anal...Airframe structural optimization at different design stages results in new mass and stiffness distributions which modify the critical design loads envelop. Determination of aircraft critical loads is an extensive analysis procedure which involves simulating the aircraft at thousands of load cases as defmed in the certification requirements. It is computationally prohibitive to use a GFEM （Global Finite Element Model） for the load analysis, hence reduced order structural models are required which closely represent the dynamic characteristics of the GFEM. This paper presents the implementation of CMS （Component Mode Synthesis） method for the generation of high fidelity ROM （Reduced Order Model） of complex airframes. Here, sub-structuring technique is used to divide the complex higher order airframe dynamical system into a set of subsystems. Each subsystem is reduced to fewer degrees of freedom using matrix projection onto a carefully chosen reduced order basis subspace. The reduced structural matrices are assembled for all the subsystems through interface coupling and the dynamic response of the total system is solved. The CMS method is employed to develop the ROM of a Bombardier Aerospace business jet which is coupled with aerodynamic model for dynamic aeroelasticity loads analysis under gust turbulence. Another set of dynamic aeroelastic loads is also generated employing a stick model of same aircraft. Stick model is the reduced order modelling methodology commonly used in the aerospace industry based on stiffness generation by unitary loading application. The extracted aeroelastic loads from both models are compared against those generated employing the GFEM. Critical loads modal participation factors and modal characteristics of the different ROMs are investigated and compared against those of the GFEM. Results obtained show that the ROM generated using Craig Bampton CMS reduction process has a superior dynamic characteristics compared to the stick model.展开更多
After corrosion and pitting corrosion, the wire nanometer phases are observed using a transmission electron microscope (TEM) in C+Ti dual implanted H13 steel. The property of corrosion resistance dual-implanted (C+Ti)...After corrosion and pitting corrosion, the wire nanometer phases are observed using a transmission electron microscope (TEM) in C+Ti dual implanted H13 steel. The property of corrosion resistance dual-implanted (C+Ti) H13 steel is studied using multi-sweep cyclic voltammetry. TEM images of the cross section of an implanted sample reveal plenty of circular nanometer structures with diameters of 10–30 nm. The phases are densely embedded in the implanted layer. The embedded structure improves the surface corrosion resistance, as can be observed with a scanning electron microscope (SEM). The phases with the shape of a tiny wire in nanometer size are formed. The nanometer phases, consisting of TiC, FeTi and FeTi2, are formed in dual implanted layer. The corrosion current peak density decreases to 1/16–1/10 that of the unimplanted H13 steel. The formation conditions of the nanometer phases and their effects are investigated. The passivation layer consists of nanometer phases. The corrosion resistance of the dual implantation can be further enhanced with an increase in ion dose.展开更多
Peptides/proteins aggregation can give rise to pathological conditions of many human diseases.Small partially ordered oligomers formed in the early stage of aggregation,rather than mature fibrils,are thought to be the...Peptides/proteins aggregation can give rise to pathological conditions of many human diseases.Small partially ordered oligomers formed in the early stage of aggregation,rather than mature fibrils,are thought to be the main toxicity agent for the living cell.Thus,understanding the pathway and the underlying physical mechanism in the early stage of aggregation is very important for prevention and treatment of these protein functional diseases.Herein we use all-atom molecular dynamics simulations to study the aggregation of four NFGAIL hexapeptides(NFGAIL peptide is a core segment of human islet amyloid polypeptide and exhibits similar aggregation kinetics as the full-length polypeptide).We observe that the peptide monomers in water mainly adopt non-structural coil configurations;the four peptides which are randomly placed in water aggregate spontaneously to partially ordered oligomer(β-sheets)through dimerization or trimerization,with the dimerization predominated.Both parallel and anti-parallelβ-sheets are observed.The hydrophobic interactions drive the initial peptides associations,and the subsequent conformational fluctuations promote the formation of more hydrogen bonds between the dangling hydrogen sites in the main chains of peptides.展开更多
文摘From the view of energy state of material, this paper introduces a concept of weathering potential in carrying out quantitative calculation of the relevant products at different stages of rock-weathering and primary soil-forming processes, elaborates respectively on weathering degree in the bio-weathering layer of rocks and during the formation of soil material and clay, and evaluats the further tendency of weathering in the above-mentioned stages. The authors have discovered that the scales of weathering potential of the materials increase successively in the three stages, which indicates that the products in the above-mentioned three stages must have undergone stronger and stronger weathering in the primitive forming process of soil in Fildes Peninsula, Antarctic. But, because of relatively weak chemical weathering, it is reasonable that there are much more skeleton grains and little clay in primary soils in this region. Meanwhile, the authors have also verified that the weathering potential of crude rock determines to some extent decrease in the products' weathering potential in the different stages in primary soil-forming, thereby plays an important role in the genesis and development of the primary soil in the studied area.
文摘Airframe structural optimization at different design stages results in new mass and stiffness distributions which modify the critical design loads envelop. Determination of aircraft critical loads is an extensive analysis procedure which involves simulating the aircraft at thousands of load cases as defmed in the certification requirements. It is computationally prohibitive to use a GFEM （Global Finite Element Model） for the load analysis, hence reduced order structural models are required which closely represent the dynamic characteristics of the GFEM. This paper presents the implementation of CMS （Component Mode Synthesis） method for the generation of high fidelity ROM （Reduced Order Model） of complex airframes. Here, sub-structuring technique is used to divide the complex higher order airframe dynamical system into a set of subsystems. Each subsystem is reduced to fewer degrees of freedom using matrix projection onto a carefully chosen reduced order basis subspace. The reduced structural matrices are assembled for all the subsystems through interface coupling and the dynamic response of the total system is solved. The CMS method is employed to develop the ROM of a Bombardier Aerospace business jet which is coupled with aerodynamic model for dynamic aeroelasticity loads analysis under gust turbulence. Another set of dynamic aeroelastic loads is also generated employing a stick model of same aircraft. Stick model is the reduced order modelling methodology commonly used in the aerospace industry based on stiffness generation by unitary loading application. The extracted aeroelastic loads from both models are compared against those generated employing the GFEM. Critical loads modal participation factors and modal characteristics of the different ROMs are investigated and compared against those of the GFEM. Results obtained show that the ROM generated using Craig Bampton CMS reduction process has a superior dynamic characteristics compared to the stick model.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59671051) "863"Project.
文摘After corrosion and pitting corrosion, the wire nanometer phases are observed using a transmission electron microscope (TEM) in C+Ti dual implanted H13 steel. The property of corrosion resistance dual-implanted (C+Ti) H13 steel is studied using multi-sweep cyclic voltammetry. TEM images of the cross section of an implanted sample reveal plenty of circular nanometer structures with diameters of 10–30 nm. The phases are densely embedded in the implanted layer. The embedded structure improves the surface corrosion resistance, as can be observed with a scanning electron microscope (SEM). The phases with the shape of a tiny wire in nanometer size are formed. The nanometer phases, consisting of TiC, FeTi and FeTi2, are formed in dual implanted layer. The corrosion current peak density decreases to 1/16–1/10 that of the unimplanted H13 steel. The formation conditions of the nanometer phases and their effects are investigated. The passivation layer consists of nanometer phases. The corrosion resistance of the dual implantation can be further enhanced with an increase in ion dose.
基金Supported by the National Natural Science Foundation of China under Grant Nos.30870593 and 11204269the China Postdoctoral Science Foundation under Grant No.2012M511351+2 种基金Zhejiang Provincial Natural Science Foundation of China under Grant No.LY12A04007the Fundamental Research Funds for the Central Universitiesthe KYLIN-I Supercomputer in Institute for Fusion Theory and Simulation,Zhejiang University
文摘Peptides/proteins aggregation can give rise to pathological conditions of many human diseases.Small partially ordered oligomers formed in the early stage of aggregation,rather than mature fibrils,are thought to be the main toxicity agent for the living cell.Thus,understanding the pathway and the underlying physical mechanism in the early stage of aggregation is very important for prevention and treatment of these protein functional diseases.Herein we use all-atom molecular dynamics simulations to study the aggregation of four NFGAIL hexapeptides(NFGAIL peptide is a core segment of human islet amyloid polypeptide and exhibits similar aggregation kinetics as the full-length polypeptide).We observe that the peptide monomers in water mainly adopt non-structural coil configurations;the four peptides which are randomly placed in water aggregate spontaneously to partially ordered oligomer(β-sheets)through dimerization or trimerization,with the dimerization predominated.Both parallel and anti-parallelβ-sheets are observed.The hydrophobic interactions drive the initial peptides associations,and the subsequent conformational fluctuations promote the formation of more hydrogen bonds between the dangling hydrogen sites in the main chains of peptides.
