Field investigation shows that the boundary between the Kuqa Basin and the Tianshan Mountains can be divided into two sections with the Yanbulak area as the di-viding point. In the western section, the Mesozoic strata...Field investigation shows that the boundary between the Kuqa Basin and the Tianshan Mountains can be divided into two sections with the Yanbulak area as the di-viding point. In the western section, the Mesozoic strata overlie unconformably on the Paleozoic rocks. The ba-sin-dipping faults developed in both Mesozoic and Paleozoic rocks. The eastern section is characterized by basin-dipping normal faults separating the Paleozoic strata and Tertiary. The brittle structural analysis was carried out along the ba-sin-range boundary. 360 measurements of striations have been obtained at a total of 25 sites. Paleostress reconstruction indicates that the basin-range boundary was in an exten-sional condition, with some superimposed strike-slip, during the Late Tertiary. The extension could be explained by the vertical block uplift of the Tianshan Mountains.展开更多
For more than 150 years, geologic characteristics claimed to be evidence for pre-Pleistocene glaciations have been debated. Advancements in recent decades, in understanding features generated by mainly glacial and mas...For more than 150 years, geologic characteristics claimed to be evidence for pre-Pleistocene glaciations have been debated. Advancements in recent decades, in understanding features generated by mainly glacial and mass flow processes, are here reviewed. Detailed studies of data offered in support of prePleistocene glaciations have led to revisions that involve environments of mass movements. Similarities and differences between Quaternary glaciogenic and mass movement features are examined, to provide a more systematic methodology for analysing the origins of more ancient deposits. Analyses and evaluation of data are from a) Quaternary glaciogenic sediments, b) formations which have been assigned to pre-Pleistocene glaciations, and c) formations with comparable features associated with mass movements(and occasionally tectonics). Multiple proxies are assembled to develop correct interpretations of ancient strata. The aim is not per se to reinterpret specific formations and past climate changes, but to enable data to be evaluated using a broader and more inclusive conceptual framework.Regularly occurring pre-Pleistocene features interpreted to be glaciogenic, have often been shown to have few or no Quaternary glaciogenic equivalents. These same features commonly form by sediment gravity flows or other non-glacial processes, which may have led to misinterpretations of ancient deposits. These features include, for example, environmental affinity of fossils, grading, bedding, fabrics, size and appearance of erratics, polished and striated clasts and surfaces(“pavements”), dropstones, and surface microtextures.Recent decades of progress in research relating to glacial and sediment gravity flow processes have resulted in proposals by geologists, based on more detailed field data, more often of an origin by mass movements and tectonism than glaciation.The most coherent data of this review, i.e., appearances of features produced by glaciation, sediment gravity flows and a few other geological processes, are summarized展开更多
For many crucial industrial applications,enzyme-catalyzed processes take place in harsh organic solvent environments.However,it remains a challenging problem to improve enzyme stability in organic solvents.This study ...For many crucial industrial applications,enzyme-catalyzed processes take place in harsh organic solvent environments.However,it remains a challenging problem to improve enzyme stability in organic solvents.This study utilized the MLDE(machine learning-assisted directed evolution)protocol to improve the methanol tolerance of Proteus mirabilis lipase(PML).The machine learning(ML)models were trained based on 266 combinatorial mutants.Using top 3 in 22 regression models based on evaluation of tenfold cross-validation,the fitness landscape of the 8000 full-space combinatorial mutants was predicted.All mutants in the restricted library showed higher methanol tolerance,among which the methanol tolerance of G202N/K208G/G266S(NGS)was up to 13-fold compared with the wild-type.Molecular dynamics(MD)simulation showed that reconstructing of critical hydrogen bond network in the mutant region of NGS provides a more stable local structure.This compact structure may improve the methanol tolerance by preventing organic solvent molecules into the activity site and resisting structural destruction.This work provides a successful case of evolution guided by ML for higher organic solvent tolerance of enzyme,and may also be a reference for broad enzyme modifications.展开更多
A macro-cell was used to study the phenomenon of anode striation on a 34 VGA Shadow Mask Plasma Display Panel （SMPDP）. The breakdown process in the sustaining period of the macro-cell was taken by an Intensified Cha...A macro-cell was used to study the phenomenon of anode striation on a 34 VGA Shadow Mask Plasma Display Panel （SMPDP）. The breakdown process in the sustaining period of the macro-cell was taken by an Intensified Charge Coupled Device（ICCD） with narrow band filters. The mechanism of formation and evolution of the anode striation on SMPDP were investigated. The influence of the width of the electrode, the sustaining voltage, sustaining frequency and the voltage of the shadow mask on the anode striation was also studied. The results showed that the width of the electrodes, the sustaining voltage and frequency had a strong influence on the anode striation. The voltage of the shadow mask, however, hardly affected the anode striation, the firing voltage or the sustaining voltage.展开更多
The nonlinear phenomenon is very popular in dielectric barrier discharge （DBD） plasmas. There are at least three kinds of spatial and temporal nonlinear phenomena appearing synchronously or asynchronously in DBDs, i...The nonlinear phenomenon is very popular in dielectric barrier discharge （DBD） plasmas. There are at least three kinds of spatial and temporal nonlinear phenomena appearing synchronously or asynchronously in DBDs, i.e. self-organized patterns, striations and chaos. This paper describes the recent research and progress in understanding the nature of these nonlinear phenomena. Patterns are macroscopic structures with certain spatial and/or temporal periodicities generated through self- organization of microscopic parameters. The physics of patterns in DBDs is mainly associated with lateral dynamic behaviors or the lateral non-local effect of charged particles resulting in the lateral development or non-uniformity of discharge. Striations are ionization waves with unique properties determined by transport phenomena, ionization processes and electron kinetics in current-carrying plasmas. The physics of striations in DBDs is mainly associated with the advances in non-local electron kinetics in spatially inhomogeneous plasmas. Chaos is a kind of random and non-periodic phenomenon occunfng in a determined dynamic system, following a series of certain rules while exhibiting random locomotion, and is regarded as an intrinsic and ubiquitous phenomenon in a nonlinear dynamic system. An evolution trajectory including period-doubling bifurcation to chaos was observed in DBDs or DBD-derived plasmas. In a common sense, it is believed that the formation of all the three nonlinear phenomena in a DBD system should be related to the non-local transversal and/or longitudinal dynamics of space charges （i.e. non-local effect） or the localized electric field interaction. Future work is still needed on the underlying physics and should be directed to pursuing the unification of these nonlinear phenomena in DBD.展开更多
In this work,striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision（PIC/MCC）simulation.The spatio-temporal evolution of the potential and the electron energy durin...In this work,striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision（PIC/MCC）simulation.The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed.The processes of striation formation in pulsed glow discharges and dielectric barrier discharges（DBD）are compared.The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other.The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge.During a pulsed breakdown,the striations are formed one by one towards the anode in a weak field channel.This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons.展开更多
SEM photos for very coarse grained and high ductile polycrystalline pure Al show following characteristics:A few fracture sources are concentrated,the crack propagates in fan-shape near them,and the fatigue striations...SEM photos for very coarse grained and high ductile polycrystalline pure Al show following characteristics:A few fracture sources are concentrated,the crack propagates in fan-shape near them,and the fatigue striations are cyclic cleavage facets.Each striation consists of a wide cleavage facet and a narrow cleavage stage.Those stages often blunt due to plastic deformation.The fatigue striations are clear and continual,and distribute over whole zone of stage Ⅱ crack propagation.Two kinds of fatigue striations form in different levels,are conjoined by a“twisted baked piece of pastry”band.The secondary crack along the fatigue striations was observed frequently.Some of them have already developed into secondary macrocracks and secondary fatigue striations were found clearly on secondary fracture sur- face.The fracture surface can be divided into two parts,initiation and propagation zone of the crack,however,no statical-fracture zone was observed.The mechanism to form striations was preliminarily discussed.展开更多
Kunming basin is a Cenozoic faulted basin under the control of mainly SN-trending active faults. In and around the basin, there are a total of eight major active faults. Seismo-geological survey and fault slip observa...Kunming basin is a Cenozoic faulted basin under the control of mainly SN-trending active faults. In and around the basin, there are a total of eight major active faults. Seismo-geological survey and fault slip observation show that the SN- and NE-trending active faults are mostly sinistral strike-slip faults, while the NW-trending faults are mostly dextral strike-slip faults. Using stress tensor inversion method with 706 active fault striation data at 22 measurement sites, we determined tectonic stress field of the study area. The result shows that modern tectonic stress field in and around Kunming basin is characterized by NNW-SSE compression, ENE-WSW extension, and strike-slip stress regimes. The maximum principal compressional stress （σ1） is oriented 335o;o, with an average dip angle of 21°; the minimum （σ3） is oriented 44o;3o, with an average dip angle of 14°, and the intermediate （σ2） has a high, or nearly vertical, dip angle. The inversion result from fault slip data is consistent with the result from focal mechanism solutions.展开更多
Metal laser cutting belongs to mature laser material processing technologies in industry applications. However, without understanding of the mechanism underlying the overall process, the improvement of the cutting qua...Metal laser cutting belongs to mature laser material processing technologies in industry applications. However, without understanding of the mechanism underlying the overall process, the improvement of the cutting quality is restricted. In this paper, an instantaneous melt removal model is presented to describe the process of material removal and striation formation. In the temperature field calculation, melted metal layer is removed when it grows to an assumed thickness. The effects of cutting parameters including cutting speed, gas pressure and laser power on the shape of striation are discussed. A novel method of getting striation free cutting surface is presented. Finally, laser cutting experiments of mild steel is conducted to validate the model. The striation variation trend can be well predicted by the model presented here and the disagreement may be caused by the coupling effect of cutting speed and critical thickness value.展开更多
文摘Field investigation shows that the boundary between the Kuqa Basin and the Tianshan Mountains can be divided into two sections with the Yanbulak area as the di-viding point. In the western section, the Mesozoic strata overlie unconformably on the Paleozoic rocks. The ba-sin-dipping faults developed in both Mesozoic and Paleozoic rocks. The eastern section is characterized by basin-dipping normal faults separating the Paleozoic strata and Tertiary. The brittle structural analysis was carried out along the ba-sin-range boundary. 360 measurements of striations have been obtained at a total of 25 sites. Paleostress reconstruction indicates that the basin-range boundary was in an exten-sional condition, with some superimposed strike-slip, during the Late Tertiary. The extension could be explained by the vertical block uplift of the Tianshan Mountains.
文摘For more than 150 years, geologic characteristics claimed to be evidence for pre-Pleistocene glaciations have been debated. Advancements in recent decades, in understanding features generated by mainly glacial and mass flow processes, are here reviewed. Detailed studies of data offered in support of prePleistocene glaciations have led to revisions that involve environments of mass movements. Similarities and differences between Quaternary glaciogenic and mass movement features are examined, to provide a more systematic methodology for analysing the origins of more ancient deposits. Analyses and evaluation of data are from a) Quaternary glaciogenic sediments, b) formations which have been assigned to pre-Pleistocene glaciations, and c) formations with comparable features associated with mass movements(and occasionally tectonics). Multiple proxies are assembled to develop correct interpretations of ancient strata. The aim is not per se to reinterpret specific formations and past climate changes, but to enable data to be evaluated using a broader and more inclusive conceptual framework.Regularly occurring pre-Pleistocene features interpreted to be glaciogenic, have often been shown to have few or no Quaternary glaciogenic equivalents. These same features commonly form by sediment gravity flows or other non-glacial processes, which may have led to misinterpretations of ancient deposits. These features include, for example, environmental affinity of fossils, grading, bedding, fabrics, size and appearance of erratics, polished and striated clasts and surfaces(“pavements”), dropstones, and surface microtextures.Recent decades of progress in research relating to glacial and sediment gravity flow processes have resulted in proposals by geologists, based on more detailed field data, more often of an origin by mass movements and tectonism than glaciation.The most coherent data of this review, i.e., appearances of features produced by glaciation, sediment gravity flows and a few other geological processes, are summarized
基金the National Natural Science Foundation of China(No.22078129)the Fundamental Research Funds for the Central Universities(No.JUSRP121014).
文摘For many crucial industrial applications,enzyme-catalyzed processes take place in harsh organic solvent environments.However,it remains a challenging problem to improve enzyme stability in organic solvents.This study utilized the MLDE(machine learning-assisted directed evolution)protocol to improve the methanol tolerance of Proteus mirabilis lipase(PML).The machine learning(ML)models were trained based on 266 combinatorial mutants.Using top 3 in 22 regression models based on evaluation of tenfold cross-validation,the fitness landscape of the 8000 full-space combinatorial mutants was predicted.All mutants in the restricted library showed higher methanol tolerance,among which the methanol tolerance of G202N/K208G/G266S(NGS)was up to 13-fold compared with the wild-type.Molecular dynamics(MD)simulation showed that reconstructing of critical hydrogen bond network in the mutant region of NGS provides a more stable local structure.This compact structure may improve the methanol tolerance by preventing organic solvent molecules into the activity site and resisting structural destruction.This work provides a successful case of evolution guided by ML for higher organic solvent tolerance of enzyme,and may also be a reference for broad enzyme modifications.
基金supported by the National Natural Science Foundation of China(Nos.60271016 and 60271033)
文摘A macro-cell was used to study the phenomenon of anode striation on a 34 VGA Shadow Mask Plasma Display Panel （SMPDP）. The breakdown process in the sustaining period of the macro-cell was taken by an Intensified Charge Coupled Device（ICCD） with narrow band filters. The mechanism of formation and evolution of the anode striation on SMPDP were investigated. The influence of the width of the electrode, the sustaining voltage, sustaining frequency and the voltage of the shadow mask on the anode striation was also studied. The results showed that the width of the electrodes, the sustaining voltage and frequency had a strong influence on the anode striation. The voltage of the shadow mask, however, hardly affected the anode striation, the firing voltage or the sustaining voltage.
基金National Natural Science Foundation of China for continuous financial support under Grant Nos. 10475007, 10875010, 11175017 and 51607074the State Education Ministry of China under Grant No. NCET-05-0176
文摘The nonlinear phenomenon is very popular in dielectric barrier discharge （DBD） plasmas. There are at least three kinds of spatial and temporal nonlinear phenomena appearing synchronously or asynchronously in DBDs, i.e. self-organized patterns, striations and chaos. This paper describes the recent research and progress in understanding the nature of these nonlinear phenomena. Patterns are macroscopic structures with certain spatial and/or temporal periodicities generated through self- organization of microscopic parameters. The physics of patterns in DBDs is mainly associated with lateral dynamic behaviors or the lateral non-local effect of charged particles resulting in the lateral development or non-uniformity of discharge. Striations are ionization waves with unique properties determined by transport phenomena, ionization processes and electron kinetics in current-carrying plasmas. The physics of striations in DBDs is mainly associated with the advances in non-local electron kinetics in spatially inhomogeneous plasmas. Chaos is a kind of random and non-periodic phenomenon occunfng in a determined dynamic system, following a series of certain rules while exhibiting random locomotion, and is regarded as an intrinsic and ubiquitous phenomenon in a nonlinear dynamic system. An evolution trajectory including period-doubling bifurcation to chaos was observed in DBDs or DBD-derived plasmas. In a common sense, it is believed that the formation of all the three nonlinear phenomena in a DBD system should be related to the non-local transversal and/or longitudinal dynamics of space charges （i.e. non-local effect） or the localized electric field interaction. Future work is still needed on the underlying physics and should be directed to pursuing the unification of these nonlinear phenomena in DBD.
基金supported by National Natural Science Foundation of China(Nos.10875010 and 11175017)
文摘In this work,striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision（PIC/MCC）simulation.The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed.The processes of striation formation in pulsed glow discharges and dielectric barrier discharges（DBD）are compared.The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other.The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge.During a pulsed breakdown,the striations are formed one by one towards the anode in a weak field channel.This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons.
文摘SEM photos for very coarse grained and high ductile polycrystalline pure Al show following characteristics:A few fracture sources are concentrated,the crack propagates in fan-shape near them,and the fatigue striations are cyclic cleavage facets.Each striation consists of a wide cleavage facet and a narrow cleavage stage.Those stages often blunt due to plastic deformation.The fatigue striations are clear and continual,and distribute over whole zone of stage Ⅱ crack propagation.Two kinds of fatigue striations form in different levels,are conjoined by a“twisted baked piece of pastry”band.The secondary crack along the fatigue striations was observed frequently.Some of them have already developed into secondary macrocracks and secondary fatigue striations were found clearly on secondary fracture sur- face.The fracture surface can be divided into two parts,initiation and propagation zone of the crack,however,no statical-fracture zone was observed.The mechanism to form striations was preliminarily discussed.
基金Special Fund for Scientific Research Institutions at Central Level (ZDJ2007-8)a Project sponsored by the Minis-try of Science and Technology of P. R. China (2006BAC13B01)
文摘Kunming basin is a Cenozoic faulted basin under the control of mainly SN-trending active faults. In and around the basin, there are a total of eight major active faults. Seismo-geological survey and fault slip observation show that the SN- and NE-trending active faults are mostly sinistral strike-slip faults, while the NW-trending faults are mostly dextral strike-slip faults. Using stress tensor inversion method with 706 active fault striation data at 22 measurement sites, we determined tectonic stress field of the study area. The result shows that modern tectonic stress field in and around Kunming basin is characterized by NNW-SSE compression, ENE-WSW extension, and strike-slip stress regimes. The maximum principal compressional stress （σ1） is oriented 335o;o, with an average dip angle of 21°; the minimum （σ3） is oriented 44o;3o, with an average dip angle of 14°, and the intermediate （σ2） has a high, or nearly vertical, dip angle. The inversion result from fault slip data is consistent with the result from focal mechanism solutions.
文摘Metal laser cutting belongs to mature laser material processing technologies in industry applications. However, without understanding of the mechanism underlying the overall process, the improvement of the cutting quality is restricted. In this paper, an instantaneous melt removal model is presented to describe the process of material removal and striation formation. In the temperature field calculation, melted metal layer is removed when it grows to an assumed thickness. The effects of cutting parameters including cutting speed, gas pressure and laser power on the shape of striation are discussed. A novel method of getting striation free cutting surface is presented. Finally, laser cutting experiments of mild steel is conducted to validate the model. The striation variation trend can be well predicted by the model presented here and the disagreement may be caused by the coupling effect of cutting speed and critical thickness value.
