期刊文献+
共找到63,251篇文章
< 1 2 250 >
每页显示 20 50 100
Breakthrough of shallow shale gas exploration in Taiyang anticline area and its significance for resource development in Zhaotong, Yunnan Province, China 认领
1
作者 LIANG Xing XU Zhengyu +8 位作者 ZHANG Zhao WANG Weixu ZHANG Jiehui LU Huili ZHANG Lei ZOU Chen WANG Gaocheng MEI Jue RUI Yun 《石油勘探与开发:英文版》 2020年第1期12-29,共18页
Based on exploration and development results and evaluation of marine shale gas in South China in the past ten years, in view of the features of "high maturity, strong tectonic reformation and high shear stress&q... Based on exploration and development results and evaluation of marine shale gas in South China in the past ten years, in view of the features of "high maturity, strong tectonic reformation and high shear stress" of the shale in Zhaotong exploration zone in the Yunnan and Guizhou Plateau, as well as the key issues of long time diffusion and leakage of shallow shale gas, and the preservation conditions, the factors controlling shallow shale gas sweet spot and key zone selection evaluation technology of shale gas are investigated. From 2017 to 2018, the first significant exploration breakthrough was made in the Taiyang anticline at a buried depth of 700 to 2 000 m, discovering large-scale proved geological reserves of shallow shale gas. By examining the accumulation conditions and sweet spot control factors of the shallow shale gas in this area, it is found that the accumulation and productivity potential of shale gas in the mountainous area with complex structure outside basin are controlled by five factors:(1) The gas-rich area has weak tectonic reformation and good preservation conditions on the whole, taking on typical anticline trap occurrence mode.(2) The gas-rich area is in over-pressure state and high in shale gas content.(3) The gas-rich area has high quality shale and thus superior source rock condition.(4) The gas-rich area has high quality reservoirs dominated by class I.(5) The shale gas reservoir in the gas-rich area has high content of brittle minerals and small difference between maximum and minimum horizontal stresses which are conducive to hydraulic fracturing. The innovative practice and core technologies formed during the exploration and production capacity construction of shallow shale gas in the Zhaotong demonstration zone have great reference significance for shallow shale gas exploration and development in other areas. 展开更多
关键词 SHALLOW shale gas SILURIAN Longmaxi FORMATION Ordovician Wufeng FORMATION EXPLORATION BREAKTHROUGH Taiyang ANTICLINE area Zhaotong area ANTICLINE
在线阅读 免费下载
Cooperative formation control of multiple aerial vehicles based on guidance route in a complex task environment 认领
2
作者 Guibin SUN Rui ZHOU +4 位作者 Kun XU Zhi WENG Yuhang ZHANG Zhuoning DONG Yingxun WANG 《中国航空学报:英文版》 SCIE EI CAS CSCD 2020年第2期701-720,共20页
In recent years,formation control of multi-agent has been a significant research subject in the field of cooperative control.However,previous works have mainly concentrated on formation control for simple point-mass m... In recent years,formation control of multi-agent has been a significant research subject in the field of cooperative control.However,previous works have mainly concentrated on formation control for simple point-mass model and linear model.In contrast,this paper presents a novel cooperative algorithm for multiple air vehicles formation control,which aims to devise a control strategy based on guidance route to achieve precisely coordinated formation control for a group of fixed-wing aircraft in a complex task environment.The proposed method introduces the leader-follower structure for effective organization of the multi-agent coordination.Moreover,the Partial Integrated Formation and Control(PIFC)is adopted to design the control law for Guidance-Route based Formation Control(GRFC).Additionally,the proposed approach designs two guidance-route generation strategies for two special situations to demonstrate the effectiveness of GRFC in complex task environments.Theoretical analysis reveals that the proposed control protocol for guidance command can ensure the overall stability and tracking accuracy of the system.Numerical simulations are performed to illustrate the theoretical results,and verify that the proposed approach can achieve coordinated formation control precisely in a complex task environment. 展开更多
关键词 COMPLEX TASK environments COOPERATIVE FORMATION control Fixed-wing aircraft GUIDANCE ROUTE Leader-follower structure Partial integrated FORMATION and control
Hydrocarbon generation and storage mechanisms of deepwater shelf shales of Ordovician Wufeng Formation–Silurian Longmaxi Formation in Sichuan Basin, China 认领
3
作者 GUO Xusheng LI Yuping +5 位作者 BORJIGEN Tenger WANG Qiang YUAN Tao SHEN Baojian MA Zhongliang WEI Fubin 《石油勘探与开发:英文版》 2020年第1期204-213,共10页
As the hydrocarbon generation and storage mechanisms of high quality shales of Upper Ordovician Wufeng Formation– Lower Silurian Longmaxi Formation remain unclear, based on geological conditions and experimental mode... As the hydrocarbon generation and storage mechanisms of high quality shales of Upper Ordovician Wufeng Formation– Lower Silurian Longmaxi Formation remain unclear, based on geological conditions and experimental modelling of shale gas formation, the shale gas generation and accumulation mechanisms as well as their coupling relationships of deep-water shelf shales in Wufeng–Longmaxi Formation of Sichuan Basin were analyzed from petrology, mineralogy, and geochemistry. The high quality shales of Wufeng–Longmaxi Formation in Sichuan Basin are characterized by high thermal evolution, high hydrocarbon generation intensity, good material base, and good roof and floor conditions;the high quality deep-water shelf shale not only has high biogenic silicon content and organic carbon content, but also high porosity coupling. It is concluded that:(1) The shales had good preservation conditions and high retainment of crude oil in the early times, and the shale gas was mainly from cracking of crude oil.(2) The biogenic silicon(opal A) turned into crystal quartz in early times of burial diagenesis, lots of micro-size intergranular pores were produced in the same time;moreover, the biogenic silicon frame had high resistance to compaction, thus it provided the conditions not only for oil charge in the early stage, but also for formation and preservation of nanometer cellular-like pores, and was the key factor enabling the preservation of organic pores.(3) The high quality shale of Wufeng–Longmaxi Formation had high brittleness, strong homogeneity, siliceous intergranular micro-pores and nanometer organic pores, which were conducive to the formation of complicated fissure network connecting the siliceous intergranular nano-pores, and thus high and stable production of shale gas. 展开更多
关键词 hydrocarbon generation and STORAGE mechanism Upper ORDOVICIAN Wufeng FORMATION Lower SILURIAN Longmaxi FORMATION deep-water SHELF siliceous shale Sichuan Basin pore preservation
在线阅读 免费下载
文章速递Biochemical Factors Affecting the Quality of Products and the Technology of Processing Deep-Sea Fish, the Giant Grenadier Albatrossia pectoralis 认领
4
作者 PIVNENKO TN KARPENKO YuV +2 位作者 KRASHCHENKO VV POZDNYAKOVA YuM ESIPENKO RV 《中国海洋大学学报:英文版》 SCIE CAS CSCD 2020年第3期681-690,共10页
The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a h... The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a higher moisture content(91.7%) and lower protein(7.4%) and lipid(0.3%) contents. The factors responsible for the softening and moisture separation during processing of grenadier are identified. Contents of some fractions of non-protein nitrogenous components, including trimethylamine oxide(TMAO) and free amino acids, are clarified. The proportion of the main myofibrillar proteins myosin and actin, which is considered as an indicator of efficiency of structure formation in fish muscle tissue during processing, is almost 20% lower in giant grenadier than in pollock. The effects of endogenous protease, Са~(2+)-ATPase and transglutaminase on the processes of autolysis, denaturation, and possibility of myofibrillar proteins cross-linking were also studied. The proposed technology of getting a nutritionally balanced, gel-like, ready-to-use foodstuff from grenadier fillet includes its enrichment with pollock muscle tissue and supplementing with a binary structure-forming agent containing collagen and chitosan. Nutritional value of the products is assessed by the method of biological assay and by determining the denaturation changes of myofibrillar proteins. The modes of fine mincing and thermal processing, as well as the shelf-life of the finished product are justified. The developed technology of producing a ready-to-eat food from giant grenadier will allow a more efficient use of this underutilized resource. 展开更多
关键词 giant grenadier Alaska pollock myosin actin proteases ATPase transglutaminase softening structure formation ready-to-eat foodstuffs
在线阅读 下载PDF
文章速递环状RNA及其在生殖发育中的研究进展 认领
5
作者 陈慧芳 杨天浩 +2 位作者 蔡健锋 李超 白银山 《畜牧兽医学报》 CAS CSCD 北大核心 2020年第9期2039-2047,共9页
环状RNA(circular RNA,circ-RNA)是一类由初始转录RNA反向剪接,形成的闭合环状RNA分子,广泛存在于真核细胞中。因不受RNA外切酶切割,所以稳定存在时间长。主要通过海绵吸附作用竞争性结合miRNA调节基因表达。circ-RNA分子鉴定及其生理... 环状RNA(circular RNA,circ-RNA)是一类由初始转录RNA反向剪接,形成的闭合环状RNA分子,广泛存在于真核细胞中。因不受RNA外切酶切割,所以稳定存在时间长。主要通过海绵吸附作用竞争性结合miRNA调节基因表达。circ-RNA分子鉴定及其生理调控作用成为近几年生命科学领域的研究热点,本文从circ-RNA的生成过程、在早期胚胎发育调控以及配子发育过程中的数量和作用等方面进行了综述。 展开更多
关键词 环状RNA 生成过程 生殖发育 基因表达
在线阅读 下载PDF
文章速递Predicting the present-day in situ stress distribution within the Yanchang Formation Chang 7 shale oil reservoir of Ordos Basin, central China 认领
6
作者 Wei Ju Xiao‑Bing Niu +4 位作者 Sheng‑Bin Feng Yuan You Ke Xu Geof Wang Hao‑Ran Xu 《石油科学:英文版》 SCIE CAS CSCD 2020年第4期912-924,共13页
The Yanchang Formation Chang 7 oil-bearing layer of the Ordos Basin is important in China for producing shale oil.The present-day in situ stress state is of practical implications for the exploration and development o... The Yanchang Formation Chang 7 oil-bearing layer of the Ordos Basin is important in China for producing shale oil.The present-day in situ stress state is of practical implications for the exploration and development of shale oil;however,few studies are focused on stress distributions within the Chang 7 reservoir.In this study,the present-day in situ stress distribution within the Chang 7 reservoir was predicted using the combined spring model based on well logs and measured stress data.The results indicate that stress magnitudes increase with burial depth within the Chang 7 reservoir.Overall,the horizontal maximum principal stress(SHmax),horizontal minimum principal stress(Shmin) and vertical stress(Sv) follow the relationship of Sv≥SHmax>Shmin,indicating a dominant normal faulting stress regime within the Chang 7 reservoir of Ordos Basin.Laterally,high stress values are mainly distributed in the northwestern parts of the studied region,while low stress values are found in the southeastern parts.Factors influencing stress distributions are also analyzed.Stress magnitudes within the Chang 7 reservoir show a positive linear relationship with burial depth.A larger value of Young's modulus results in higher stress magnitudes,and the differential horizontal stress becomes higher when the rock Young's modulus grows larger. 展开更多
关键词 Present-day in situ stress Chang 7 shale oil reservoir Influencing factor Ordos Basin Stress distribution prediction Yanchang Formation
文章速递Geochemical characteristics and genetic mechanism of the high-N2 shale gas reservoir in the Longmaxi Formation, Dianqianbei Area, China 认领
7
作者 Ji‑Lin Li Ting‑Shan Zhang +6 位作者 Yan‑Jun Li Xing Liang Xin Wang Jie‑Hui Zhang Zhao Zhang Hong‑Lin Shu Da‑Qian Rao 《石油科学:英文版》 SCIE CAS CSCD 2020年第4期939-953,共15页
As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration ri... As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration risk.Accordingly,this study explores the genesis of shale gas reservoir and the mechanism of nitrogen enrichment through investigating shale gas compositions,isotope features,and geochemical characteristics of associated gases.The high-nitrogen shale gas reservoir in the Longmaxi Formation is demonstrated to be a typical dry gas reservoir.Specifically,the alkane carbon isotope reversal is ascribed to the secondary cracking of crude oil and the Rayleigh fractionation induced by the basalt mantle plume.Such a thermogenic oil-type gas reservoir is composed of both oil-cracking gas and kerogen-cracking gas.The normally high nitrogen content(18.05%-40.92%) is attributed to organic matter cracking and thermal ammoniation in the high-maturity stage.Specifically,the high heat flow effect of the Emeishan mantle plume exacerbates the thermal cracking of organic matter in the Longmaxi Formation shale,accompanied by nitrogen generation.In comparison,the abnormally high nitrogen content(86.79%-98.54%) is ascribed to the communication between the atmosphere and deep underground fluids by deep faults,which results in hydrocarbon loss and nitrogen intrusion,acting as the key factor for deconstruction of the primary shale gas reservoir.Results of this study not only enrich research on genetic mechanism of high-maturity N_@ shale gas reservoirs,but also provide theoretical guidance for subsequent gas reservoir resource evaluation and well-drilling deployment in this area. 展开更多
关键词 Longmaxi Formation Shale gas reservoir Isotope High nitrogen content Genetic mechanism
文章速递Stability of the formation interface under the impact of hydraulic fracture propagation in the vicinity of the formation interface 认领
8
作者 Cong Lu Yun‑Xiao Lu +1 位作者 Jian‑Chun Guo Li‑ming Liu 《石油科学:英文版》 SCIE CAS CSCD 2020年第4期1101-1118,共18页
Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydr... Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydrocarbon reservoirs.Understanding the stress field and stability of the formation interface is vital to understanding stress propagation,preferably before the growing hydraulic fracture contacts the formation interface.In this study,models are developed for computing the stress field of hydraulic fracture propagation near the formation interface,and the stress fields within and at the two sides of the formation interface are analyzed.Four failure modes of the interface under the impact of hydraulic fracture propagation in its vicinity are identified,and the corresponding failure criteria are proposed.By simulating the magnitude and direction of peak stress at different parameters,the failure mode and stability of the formation interface are analyzed.Results reveal that when the interface strength is weak,the formation interface fails before the growing hydraulic fracture contacts it,and its stability is significantly related to a variety of factors,including the type of formation interface,rock mechanical properties,far-field stress,structural parameters,distance between the hydraulic fracture and formation interface,and fracturing execution parameters. 展开更多
关键词 Formation interface Fracture propagation Stress field Failure criterion Stability
Study on deuteron formation mechanism in nucleon-induced reactions 认领
9
作者 Ya-Jun He Chen-Chen Guo +2 位作者 Jun Su Long Zhu Zhen-Dong An 《核技术:英文版》 SCIE CAS CSCD 2020年第8期129-136,共8页
The mechanism of deuteron formation in neutron-induced reactions is studied within the framework of the isospin-dependent quantum molecular dynamics model,using the GEMINI code.The influence of the n+p→d reaction cha... The mechanism of deuteron formation in neutron-induced reactions is studied within the framework of the isospin-dependent quantum molecular dynamics model,using the GEMINI code.The influence of the n+p→d reaction channel is investigated by analyzing the deuteron production cross sections in the neutron-induced reactions12C(n,d),16O(n,d),and 28Si(n,d),with incident energies of 20-100 MeV.By including the n+p→d reaction channel when modeling the collision,the deuteron production cross sections increase,optimizing the cross-section results and bringing them closer to the experimental data values.This indicates that the n+p→d reaction channel is an important mechanism for enhancing deuteron production. 展开更多
关键词 Cluster mechanism Deuteron formation cross section Nucleon-induced reactions
在线阅读 下载PDF
TSPO ligands prevent the proliferation of vascular smooth muscle cells and attenuate neointima formation through AMPK activation 认领
10
作者 Lian-pan Wu Zheng-fan Gong +7 位作者 He Wang Zhong-shu Zhou Ming-ming Zhang Chao Liu Hong-mei Ren Jian Yang Yu Han Chun-yu Zeng 《中国药理学报:英文版》 SCIE CAS CSCD 2020年第1期34-46,共13页
Abnormal growth of the intimal layer of blood vessels(neointima formation)contributes to the progression of atherosclerosis and in-stent restenosis.Recent evidence shows that the 18-kDa translocator protein(TSPO),a mi... Abnormal growth of the intimal layer of blood vessels(neointima formation)contributes to the progression of atherosclerosis and in-stent restenosis.Recent evidence shows that the 18-kDa translocator protein(TSPO),a mitochondrial membrane protein,is involved in diverse cardiovascular diseases.In this study we investigated the role of endogenous TSPO in neointima formation after angioplasty in vitro and in vivo.We established a vascular injury model in vitro by using platelet-derived growth factor-BB(PDGF-BB)to stimulate rat thoracic aortic smooth muscle cells(A10 cells).We found that treatment with PDGF-BB(1-20 ng/mL)dose-dependently increased TSPO expression in A10 cells,which was blocked in the presence of PKC inhibitor or MAPK inhibitor.Overexpression of TSPO significantly promoted the proliferation and migration in A10 cells,whereas downregulation of TSPO expression by siRNA or treatment with TSPO ligands PK11195 or Ro5-4864(104 nM)produced the opposite effects.Furthermore,we found that PK11195(10?104 nM)dose-dependently activated AMPK in A10 cells.PK11195-induced inhibition on the proliferation and migration of PDGF-BB-treated A10 cells were abolished by compound C(an AMPK-specific inhibitor,103 nM).In rats with balloon-injured carotid arteries,TSPO expression was markedly upregulated in the carotid arteries.Administration of PK11195(3 mg/kg every 3 days,ip),starting from the initial balloon injury and lasting for 2 weeks,greatly attenuated carotid neointima formation by suppressing balloon injury-induced phenotype switching of VSMCs(increasedα-SMA expression).These results suggest that TSPO is a vascular injury-response molecule that promotes VSMC proliferation and migration and is responsible for the neointima formation after vascular injury,which provides a novel therapeutic target for various cardiovascular diseases including atherosclerosis and restenosis. 展开更多
关键词 NEOINTIMA formation vascular smooth muscle cells PROLIFERATION TSPO AMPK PDGF-BB PK11195 Ro5-4864 compound C balloon-injured CAROTID ARTERIES
Formation Tracking for Nonlinear Multi-agent Systems with Input and Output Quantization via Adaptive Output Feedback Control 认领
11
作者 HU Jinglin SUN Xiuxia HE Lei 《系统科学与复杂性学报:英文版》 SCIE EI CSCD 2020年第2期401-425,共25页
Signal quantization can reduce communication burden in multi-agent systems,whereas it brings control challenge to multi-agent formation tracking.This paper studies the output feedback control problem for formation tra... Signal quantization can reduce communication burden in multi-agent systems,whereas it brings control challenge to multi-agent formation tracking.This paper studies the output feedback control problem for formation tracking of multi-agent systems with both quantized input and output.The agents are described by a nonlinear dynamic model with unknown parameters and immeasurable states.To estimate immeasurable states and solve the uncertainties,state observers are developed by using dynamic high-gain tools.Through proper parameter designs,an output feedback quantized controller is established based on quantized output signals,and the quantization effect on the control system is eliminated.Stability analysis proves that,with the proposed control scheme,multi-agent systems can track the reference trajectory while forming and maintaining the desired formation shape.In addition,all the signals in the closed-loop systems are bounded.Finally,the numerical simulation and practical experiment are provided to verify the theoretical analysis. 展开更多
关键词 Adaptive output feedback formation tracking hysteretic quantizer multi-agent system
Evaluation on the natural gas hydrate formation process 认领
12
作者 Shuqi Fang Xinyue Zhang +3 位作者 Jingyi Zhang Chun Chang Pan Li Jing Bai 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2020年第3期881-888,共8页
Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compar... Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compared from six parameters,including conversion of water to hydrate,storage capacity,the rate of hydrate formation,space velocity(SV)of hydrate reaction,energy consumption and hydrate removal.The literature was selected by analyzing and comparing these six parameters mentioned above,meanwhile placing emphasis on the three parameters of storage capacity,the rate of hydrate formation and space velocity of hydrate reaction.Through analysis and comparison,four conclusions could be obtained as follows.Firstly,the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters.Secondly,the additive types,the reactor structure and the reactor size had influence on the natural gas hydrate formation process.Thirdly,the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring,spraying and static higee.Finally,it was one key for hydrate removal to realize the hydrate industrial production. 展开更多
关键词 Natural gas hydrate Evaluate Hydrate formation process Storage capacity Space velocity of hydrate reaction
在线阅读 下载PDF
Accelerated methane storage in clathrate hydrates using surfactantstabilized suspension with graphite nanoparticles 认领
13
作者 Liang Yang Xin Wang +4 位作者 Daoping Liu Guomin Cui Binlin Dou Juan Wang Shuqing Hao 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2020年第4期1112-1119,共8页
In this study,enhanced kinetics of methane hydrate formation in the sodium dodecyl sulfate(SDS)solution with different concentrations of suspended graphite nanoparticles(GNPs)were investigated at 6.1-9.0 MPa and 274.1... In this study,enhanced kinetics of methane hydrate formation in the sodium dodecyl sulfate(SDS)solution with different concentrations of suspended graphite nanoparticles(GNPs)were investigated at 6.1-9.0 MPa and 274.15 K.The GNPs with rough surfaces and excellent thermal conductivity not only provided a considerable number of microsites for hydrate nucleation but also facilitated the fast hydrate heat transfer in the suspension system.At a relatively low pressure of 6.1 MPa,the suspension with 0.4 wt%of GNPs exhibited the minimum induction time of 22 min and maximum methane uptake of 126.1 cm3·cm-3.However,the methane storage performances of the suspensions with higher and lower concentrations of GNPs were not satisfactory.At the applied pressure,the temperature increase arising from the hydrate heat in the suspension system with the optimized concentration(0.4 wt%)of GNPs was more significant than that in the traditional SDS solution.Furthermore,compared with those of the system without GNPs,enhanced hydration rate and storage capacity were achieved in the suspensions with GNPs,and the storage capacities were increased by 3.9%-17.0%.The promotion effect of GNPs on gas hydrate formation at low pressure is much more obvious than that at high pressure. 展开更多
关键词 methane storage clathrate hydrates formation kinetics SUSPENSION graphite nanoparticles
在线阅读 下载PDF
Toward accurate measurement of property-dependent galaxy clustering I.Comparison of the Vmax method and the“shuffled”method 认领
14
作者 Lei Yang Yi-Peng Jing +1 位作者 Zhi-Gang Li Xiao-Hu Yang 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2020年第4期87-98,共12页
Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure ga... Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure galaxy clustering.In this paper,by virtue of the mock galaxy catalogs,we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions(hereafter 2 PCFs),the Vmax method and the"shuffled"method.We have found that the shuffled method significantly underestimates both of the projected 2 PCFs and the two-dimensional 2 PCFs in redshift space,while the Vmax method does not show any notable bias on the 2 PCFs for volume-limited samples.For fluxlimited samples,the bias produced by the Vmax method is less than half of the shuffled method on large scales.Therefore,we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis. 展开更多
关键词 galaxies:statistics galaxies:galaxy formation and evolution large-scale structure of UNIVERSE
A new iron(Ⅲ) chelator of coprogen-type siderophore from the deep-sea-derived fungus Mycosphaerella sp. SCSIO z059 认领
15
作者 HUANG Zhong-Hui LIANG Xiao QI Shu-Hua 《中国天然药物:英文版》 SCIE CAS CSCD 2020年第4期243-249,共7页
Mycosphazine A(1), a new iron(Ⅲ) chelator of coprogen-type siderophore, and mycosphamide A(2), a new cyclic amide benzoate, together with six known aryl amides(3-8), were isolated from the fermentation broth of the d... Mycosphazine A(1), a new iron(Ⅲ) chelator of coprogen-type siderophore, and mycosphamide A(2), a new cyclic amide benzoate, together with six known aryl amides(3-8), were isolated from the fermentation broth of the deep-sea-derived fungus Mycosphaerella sp. SCSIO z059. Alkaline hydrolysis of 1 afforded a new epimer of dimerum acid, mycosphazine B(1 a), and a new bi-fusarinine-type siderophore, mycosphazine C(1 b). The planar structures of the new compounds were elucidated by extensive spectroscopic data analysis. The absolute configurations of amino acid residues in 1 a and 1 b were determined by acid hydrolysis. And the absolute configuration of 2 was established by quantum chemical calculations of the electronic circular dichroism(ECD) spectra. Compound 1 is the first siderophore-Fe(Ⅲ) chelator incorporating both L-ornithine and D-ornithine unites. Compounds 3-8 were reported as natural products for the first time, and the 1 H and 13 C NMR data of 6 and 8 were assigned for the first time. Compounds 1 and 1 a could greatly promote the biofilm formation of bacterium Bacillus amyloliquefaciens with the rate of about 249% and 524% at concentration of 100 μg·mL-1, respectively. 展开更多
关键词 Deep-sea-derived fungus Mycosphaerella sp Iron(Ⅲ)chelator Coprogen-type siderophore Cyclic amide Biofilm formation
Observations and modeling of flat subduction and its geological effects 认领
16
作者 Zhiyong YAN Lin CHEN +3 位作者 Xiong XIONG Kai WANG Renxian XIE Hou Tze HSU 《中国科学:地球科学英文版》 SCIE EI CAS CSCD 2020年第8期1069-1091,共23页
Flat subduction refers to low-angle(<10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ~10% of present-day subduction zones, but its impact on the behavior of the overri... Flat subduction refers to low-angle(<10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ~10% of present-day subduction zones, but its impact on the behavior of the overriding plate is particularly strong.For example, flat subduction zones are typically associated with stronger earthquakes. The deformation caused by typical flat subduction will transfer from the trench to the overriding continental interior and form a broad magma belt. The formation mechanism of flat subduction has been linked to the relative buoyancy of subducted oceanic plateaus, overthrusting of the overriding plate, hydrodynamic suction, and trench retreat. However, these mechanisms remain debated. This paper systematically analyzes and summarizes previous studies on flat subduction, and outlines the possible geological effects of flat subduction, such as intracontinental orogeny and magmatism. Using examples from numerical modeling, we discuss the possible formation mechanisms. The most important factors that control the formation of flat subduction are associated with overthrusting of the overriding plate and the arrival of an oceanic plateau at the subduction zone. In addition, trench retreat is necessary to enable flat subduction. Hydrodynamic suction contributes to the reduction of the slab dip angle, but is insufficient to form flat subduction. Future numerical modeling of flat subduction should carry out three-dimensional high-resolution thermo-mechanical simulation, considering the influence of crustal eclogitization(negative buoyancy) and mantle serpentinization(positive buoyancy) of oceanic lithosphere, in combination with geological and geophysical data. 展开更多
关键词 Flat subduction MAGMATISM Intracontinental orogeny Formation mechanism Numerical modeling
天然气水合物领域关键专利技术剖析 认领
17
作者 王林 《当代石油石化》 CAS 2020年第6期27-34,共8页
天然气水合物抑制技术一直是油气勘探开发行业的研究热点,近年来如何更安全、更经济、更高效地开采、分离、制备、储存和运输天然气水合物,越来越受到学术界与工业界的持续关注。文章对天然气水合物技术领域的全球专利布局情况进行了宏... 天然气水合物抑制技术一直是油气勘探开发行业的研究热点,近年来如何更安全、更经济、更高效地开采、分离、制备、储存和运输天然气水合物,越来越受到学术界与工业界的持续关注。文章对天然气水合物技术领域的全球专利布局情况进行了宏观分析,进而对被引次数最多的50件重点专利进行细致剖析,明晰了天然气水合物开采、抑制与制备技术的关键核心专利与重点专利权人,并从专利视角详细探究了该领域的技术发展路线与创新发展态势。 展开更多
关键词 天然气水合物 开采 抑制 制备 专利布局 统计分析
在线阅读 下载PDF
Formation of choroidal neovascularization under macular fovea after high-power laser irradiation: a case report 认领
18
作者 Shan-Shan Li Xiao-Ran Chu Fang Chen 《国际眼科杂志:英文版》 SCIE CAS 2020年第2期359-361,共3页
Dear Editor,I am Dr.Shan-Shan Li,from Northern Jiangsu People’s Hospital,Yangzhou,China.I write to present the case of formation of choroidal neovascularization(CNV)under the fovea after high-power laser irradiation.... Dear Editor,I am Dr.Shan-Shan Li,from Northern Jiangsu People’s Hospital,Yangzhou,China.I write to present the case of formation of choroidal neovascularization(CNV)under the fovea after high-power laser irradiation.Currently,there is an increasing availability and accessibility to laser instruments,but improper use of these tools can lead to macular damage and irreversible visual impairment. 展开更多
关键词 FFA a case report Formation of choroidal NEOVASCULARIZATION under MACULAR FOVEA AFTER HIGH-POWER laser IRRADIATION
Effect of H2 addition on process of primary slag formation in cohesive zone 认领
19
作者 Ya-na Qie Qing Lyu +2 位作者 Chen-chen Lan Shu-hui Zhang Ran Liu 《钢铁研究学报:英文版》 SCIE EI CAS CSCD 2020年第2期132-140,共9页
Based on the technology of gas-injection blast furnace(BF),the characteristics of primary slag formation with H2 addition were researched.The results indicate that,compared with traditional BF,the primary melt is form... Based on the technology of gas-injection blast furnace(BF),the characteristics of primary slag formation with H2 addition were researched.The results indicate that,compared with traditional BF,the primary melt is formed at a lower temperature,which promotes the deformation of the solid burden particles.With the increase in temperature and H2 content,the quantity of formed melt containing FeO decreases sharply,corresponding to the crystallization of solid 2CaO Si02 during reduction.A wider softening range and narrower melting zone could be found in the gas-injection BF with a higher reduction potential.The permeability of burden layer is ameliorated as a result of decreased melt quantity.The influence of H2 on the high-temperature properties of burden is not so conspicuous when the H2 addition is from 10 to 15 vol.%against 5 to 10 vol.%.What is more,the slag shows a better liquidity with the decrease in basicity,owing to the transformation of melt composition from a primary phase field with high melting point to that with low melting point.The process of slag forming in gas-injection BF is characterized by earlier melt formation,less primary slag,higher melting temperature,better permeability and better liquidity,and the phase compositions of primary slag are close to those of final slag. 展开更多
关键词 Reduction degradation Primary SLAG FORMATION MELT Hydrogen ADDITION Gas-injection BLAST FURNACE
Constraints on the Ediacaran-Cambrian boundary in deep-water realm in South China: Evidence from zircon CA-ID-TIMS U-Pb ages from the topmost Liuchapo Formation 认领
20
作者 Wei WANG Mingzhong ZHOU +4 位作者 Zhuyin CHU Junjie XU Chaofeng LI Taiyi LUO Jinghui GUO 《中国科学:地球科学英文版》 SCIE EI CAS CSCD 2020年第8期1176-1187,共12页
The placement of the Ediacaran-Cambrian boundary in deep-water realm in South China and the high-precision temporal framework for the Ediacaran-Cambrian transition in this region have not yet been completely solved. R... The placement of the Ediacaran-Cambrian boundary in deep-water realm in South China and the high-precision temporal framework for the Ediacaran-Cambrian transition in this region have not yet been completely solved. Recently, we have found two K-bentonite beds in the top of the Liuchapo Formation at the Pingyin section, Guizhou Province. It provides an opportunity for constructing the temporal framework of the transitional strata on the Yangtze Platform in South China and for determining the Ediacaran-Cambrian boundary in this area. In this study, we conducted high-precision CA-ID-TIMS U-Pb dating on zircons from the two K-bentonites. The ages of the two K-bentonites were precisely constrained at 536.40±0.47/1.1/1.2 Ma(2σ, n=7, MSWD=0.92) and 541.48±0.46/1.1/1.2 Ma(2σ, n=8, MSWD=1.3). Combining the geochronological results with organic carbon isotope data of chert in the topmost Liuchapo Formation from the section, we suggest that the EdiacaranCambrian boundary should be consistent with a significant negative organic carbon isotope excursion between the two Kbentonites. The scheme of the Ediacaran-Cambrian boundary in this study is of great significance for global correlation, and further for unravelling the information of the terminal Ediacaran-early Cambrian ocean. 展开更多
关键词 Liuchapo Formation Yangtze Platform Ediacaran-Cambrian CA-ID-TIMS Organic carbon isotope
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈