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Palynological evidence for vegetational and climatic changes from the HQ deep drilling core in Yunnan Province, China

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science China Earth sciences 2007年第8期50卷 1189-1201页

作者： XIAO XiaYun SHEN Ji WANG SuMin XIAO HaiFeng TONG GuoBang Nanjing Institute of Geography and Limnology Chinese Academy of SciencesNanjing 210008China institude of Hydrogeology and Engineering Geology Chinese Academy of Geological SciencesShijiazhuang 050061China

The high-resolution pollen study of a 737.72-m-long lake sediment core in the Heqing Basin of Yunnan Province shows that the vegetation and climate of mountains around the Heqing Basin went through six obvious changes since 2.780 Ma B.P. Namely, Pinus forest occupied most mountains around the studied area and the structure of vertical vegetational belt was simple between 2.780 and 2.729 Ma B.P., reflecting a relatively warm and dry climate. During 2.729―2.608 Ma B.P., the areas of cold-temperate conifer forest (CTCF) and Tsuga forest increased and the structure of vertical vegetational belt became clear. According to percentages of tropical and subtropical elements growing in low-altitude regions rifely increased, we speculate that the increase of CTCF and Tsuga forest areas mainly resulted from strong uplift of mountains which provided upward expanding space and growing condition for these plants. Thus, the climate of the low-altitude regions around the basin was relatively warm and humid. Between 2.608 and 1.553 Ma B.P., Pinus forest occupied most mountains around the studied area and forest line of CTCF rose, which reflects a moderately warm-dry climate on the whole. During 1.553―0.876 Ma B.P., the structure of vertical vegetational belt in mountains around the studied area became complicated and the amplitude of vegetational belts shifting up and down enlarged, which implies that the amplitude of climatic change increased, the climatic associational feature was more complex and the climate was moderately cold at a majority of the stage. During 0.876―0.252 Ma B.P., there were all vertical vegetational belts existing at present in mountains around the studied area. The elements of each belt were more abundant and complex than earlier. At different periods in the stage vertical vegetational belts occurred as expanding or shrinking, and alternated each other. The amplitude of vegetational belts shifting up and down was the maximum in the whole section. This change s

关键词： pollen record palaeovegetation palaeoclimate climatic transition Heqing Basin

A Discussion on Fault Activity Based on Cross-fault Observations in the Capital Circle Region of China and Its Relationship with Earthquakes

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Earthquake Research in China 2013年第1期27卷 52-66页

作者： Li Layue Xing Chengqi Wu Anxu Liu Xinzhong Hu Leyin Institute of Earthquake science China Earthquake Administration Earthquake Administration of Beijing Municipality The First institude of Oceanography

In this paper, we made a systematic study on more than 40 years of observational data of ten temporary fault-crossing measurement sites in the capital circle region of China. We calculated horizontal and vertical components of fault slip, and horizontal extension or compression components. Considering the tectonic characteristics of the capital circle region and regional seismicity, we analyzed the present fault activity of the capital circle region and the relationship with earthquakes. The results show the complexity of fault activity in the region： the level of activity of all faults is low, most faults are left-lateral strike-slip faults; there is less vertical activity than horizontal activity and crustal movement is controlled by horizontal movement; fault activity and earthquake activity have a certain relationship, regional fault activity increases before an earthquake, and fault activity has certain abnormal features before strong earthquakes.

关键词： Capital circle region Cross-fault measurement Fault activity Earthquakeactivity

An Angular Momentum Allocation Strategy to Extend the Available Time of GEO Navigation Satellites

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An Angular Momentum Allocation Strategy to Extend the Availa...

Performance analysis and flow mechanism of channel wing considering propeller slipstream

第十一届中国卫星导航年会

作者： Zhen Cui Bin Chen Jiajia Feng Ye Ji Weijie Liu Beijing institude of Control Engineering science and Technology on Space Intelligent Control Laboratory

In order to maintain the orbit accuracy of the GEO(geostationary orbit) navigation satellite, the thruster is not allowed to use during long-term orbital operation. The disturbance torque is absorbed

关键词： GEO navigation satellite Reaction wheel envelope Angular momentum distribution

来源： cnki会议评论

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Chinese Journal of Aeronautics 2023年第11期36卷 165-184页

作者： Xiaoxuan MENG Ziyi XU Min CHANG Junqiang BAI School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Unmanned System Research Institute Northwestern Polytechnical UniversityXi’an 710072China Shenzhen Research institude of Northwestern Polytechnical University Shenzhen 518057China

The development of the Urban Air Mobility concept has proposed stringent requirements for the fixed-wing vehicle’s Short/Vertical Take-Off and Landing(S/VTOL)*** its lift-enhancing impact,the channel wing,can improve aircraft low-speed performance and Short Take-Off and Landing(STOL)*** is critical for the performance analysis and flow mechanism study of a channel wing that considers the influence of propeller slipstream to guide the design of S/VTOL *** law and mechanism for the effect of the enclosing angle of the arc wing,the phase angle of the propeller,the tip clearance,the rotational speed and the chordwise position of the propeller on the channel wing are explored utilizing the quasi-steady multi reference frame method.A channel wing with a larger enclosing angle has a better ability to enhance lift and reduce drag using propeller *** effect of propeller phase angle on channel wing aerodynamic forces is periodic and *** propeller rotational speed is helpful to enhance lift and resist flow separation for channel *** can reduce drag for tractor configuration but increase drag for pusher ***,the nose-down pitching moment of a channel wing will grow dramatically,making longitudinal trimming in aircraft layout design challenging.

关键词： Channel wing Computational fluid dynamics Flow interactions Mechanisms Slipstream effect

Visualization Investigation on Flowing Condensation in Horizontal Small Channels with Liquid Separator

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Journal of Thermal science 2018年第1期27卷 48-54页

作者： ZHANG Xuan JIA Li DANG Chao PENG Qi institude of Thermal Engineering School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing key laboratory of flow and heat transfer of phase changing in micro and small scale Beijing 100044China

A simultaneous visualization and measurement experiment was carried out to investigate condensation flow pat- terns and condensing heat transfer characteristics of refrigerant R14 lb in parallel horizontal multi-channels with liquid-vapor separator. The hydraulic diameter of each channel was 1.5 mm and the channel length was 100 ram. The refrigerant vapor flowing in the small channels was cooled by cooling water. The parallel horizontal mul- ti-channels were covered with a transparent silica glass for visualization of flow patterns. Experiments were per- formed at different inlet superheat temperatures （ranging from 3~C to 7~C）. Mass velocity was in the range of 82.37 kg mZs1 to 35.56 kg m-2s1. It was found that there were three different flow patterns through the mul- ti-channels with the increase of mass velocity. The flow patterns in each channel pass almost tended to be same and all of them were annular flows.＇ The efficiency of the liquid-vapor separator with U-type was related to vapor mass velocity and the pressure in the small channels. It was also found that the heat transfer coefficient increased with the increase of the mass velocity while the cooling water mass flow rate increased. It increased to a top point and then decreased. It increased with the increase of superheat in the low superheat temperature region.

关键词： condensation visualization multi-channels liquid-vapor separation

Kinetics and fractionation of hydrogen isotopes during gas formation from representative functional groups

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Petroleum science 2021年第4期18卷 1021-1032页

作者： Shuang-Fang Lu Guo-Qi Feng Ming-Li Shao Ji-Jun Li Hai-Tao Xue Min Wang Fang-Wen Chen Wen-Biao Li Xiao-Ting Pang aResearch Institute of Unconventional Oil&Gas and New Energy China University of PetroleumQingdaoShandong 266580China Exploitation and Development Research institude of Jilin Oilfield Company CNPCSongyuanJilin138000China

A gold tube simulation device was used to study the cleavage of representative compounds into *** goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during *** chromatography and isotopic analyses were conducted to determine how the yield of natural gas components and their hydrogen isotopic composition were related to experimental temperature and heating rate.A chemical kinetic model for the generation of each component of the natural gas and for the hydrogen isotopic fractionation was established and calibrated based on the *** indicate that the hydrogen isotopic fractionation during the evolution of various gas-forming organic materials can be satisfactorily described by chemical kinetic *** regular methane generation,the reactions at low-activation-energy region had a greater contribution than the high-activation-energy *** the reactions with high-activation-energy region had greater contribution of deuterium-rich *** with carbon isotope fractionation,this results in a greater hydrogen isotopic fractionation,which is more sensitive to changes in *** study lays a foundation for further investigations of genesis and maturity of natural gas provided by hydrogen isotopic *** also provides fundamental knowledge for investigating the filling history of natural gas reservoir and for identifying.

关键词： Gas-forming compounds Pyrolysis Hydrogen isotopes Fractionation Chemical kinetics

Mechanism and kinetics for scavenging superoxide anion by progesterone

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Chinese science Bulletin 2001年第2期46卷 117-121页

作者： SONG Junfeng SHAO Yong GUO Wei Institute of Electroanalytical Chemistry Northwest UniversityXi’an 710069China Department of Merterial and Chemical Engineering Sichuan Institude of Light Industry and Chemical TechnologyZigong 643033China

The chemical reaction of progesterone with su-peroxide anion O2- in 0.1 mol/L NaHCO3 medium is studied by polarography. Differing from the indirect inhibition of O2- generation by synthesized glucocorticoids in mecha-nism, the function that progesterone scavenges O2- is as-cribed to that O2- directly oxidizes the C =C double bond conjugated with the carbonyl moiety of progesterone mole-cule to a free radical, and then is reduced to H2O2. The result obtained in this work gives new evidence for biomedical research. The equation of rate constant of the oxidization reaction is deduced, and the apparent rate constant obtained is308 L·mol-1·s-1.

关键词： superoxide progesterone scavenging kinetics anti-oxidation.

Determining heating pipe temperature in greenhouse using proportional integral plus feedforward control and radial basic function neural-networks

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Journal of Zhejiang University-science A(Applied Physics & Engineering) 2005年第4期6卷 265-269页

作者：余朝刚应义斌王剑平杨佳 institude of Modern Agricultural Equipment and Automation Zhejiang University Department of Agriculture Electric Engineering Talimu Agriculture University

Proportional integral plus feedforward (PI+FF) control was proposed for identifying the pipe temperature in hot water heating greenhouse. To get satisfying control result, ten coefficients must be adjusted properly. The data for training and testing the radial basic function (RBF) neural-networks model of greenhouse were collected in a 1028 m2 multi-span glasshouse. Based on this model, a method of coefficients adjustment is described in this article.

关键词： PI control Greenhouse Temperature Neural networks

EXISTENCE OF SIGN-CHANGING SOLUTION FOR THREE-POINT BOUNDARY VALUE PROBLEM

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Annals of Differential Equations 2007年第2期23卷 149-158页

作者： Li Chunyan Liu Bing Dept. of Math. Henan Institude of Science and Technologg Xinziang 453000Henan Dept. of Math. ttuazhong University of Science and Technology Wuhan 430074

In this paper, by using the fixed-point index theory, we study the existence of sign-changing solution to some three-point boundary value problem{y″（t）＋f（y）=0,t∈[0,1],y（0）=0,y′（1）=αy′（η）,where 0〈α〈... 详细信息

关键词： three-point boundary problem sign-changing-solution thefixed-point index