检索结果-南通市图书馆

In situ simultaneous determination of trace elements,U-Pb and Lu-Hf isotopes in zircon and baddeleyite

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

In situ simultaneous determination of trace elements,U-Pb an...

中国科学院地质与地球物理研究所2008学术年会

作者： XIE LieWen,ZHANG YanBin,ZHANG HuiHuang,SUN JingFeng & wu FuYuan state key {3. of Lithospheric Evolution,institute of Geology and Geophysics,chinese academy of sciences,beijing 100029, china

This paper describes a combined method of simultaneously measuring U-Pb and Lu-Hf isotopes as well as trace elements in Phalaborwa baddeleyite and 91500,GJ-1,TEMORA-1 and SK10-2 zircons by means of Neptune MC-ICPMS and Agilent Q-ICPMS connected to a 193.nm excimer laser ablation system. Material ablated by laser was carried in different proportions into Q-ICPMS for U-Pb isotopic and trace elemental and MC-ICPMS for Lu-Hf isotopic *** indicate that different proportions of ablated material for the Q-ICPMS and MC-ICPMS(6:4,5:5 and 4:6 respectively) do not show any bias for the zircon/baddeleyite U-Pb age,Lu-Hf isotope and trace elemental compositions within analytical *** 40—60μm spot size,the obtained U-Pb ages of Phalaborwa baddeleyite,91500, GJ-1,TEMORA and SK10-2 zircons are 2065±15(2σ,n=20),1063.6(2a,n=19),613.6(2a,n=20),416±5 (2σ,n=20) and 3..6±0.5(2σ,n=20) Ma,*** Hf/Hf ratios are 0.28123.±24(2SD,n=20), 0.2823.0±3.(2SD,n=19),0.282028±3.(2SD,n=20),0.282687±3.(2SD,n=20) and 0.282752±53.2SD, n=20),*** obtained trace elemental compositions are identical to the reference values. Therefore,this kind of technique makes it possible to simultaneously obtain the U-Pb age,Lu-Hf isotopes and trace elemental compositions of zircon and baddeleyite,which could be an important tool in solving problems in earth sciences.

关键词： U-Pb age Lu-Hf isotopes trace elements zircon in situ measurement

Weakening Trend in the Atmospheric Heat Source over the Tibetan Plateau during Recent ***Ⅱ:Connection with Climate Warming

在线全文

cnki会议

学校读者我要写书评

暂无评论

Weakening Trend in the Atmospheric Heat Source over the Tibe...

“2010年北京气象学会中青年优秀论文评选”学术研讨会

作者： ANMIN DUAN AND GUOXIONG wu state key {3. of Numerical Modelling for Atmospheric sciences and Geophysical Fluid.Dynamics, institute of Atmospheric Physics,chinese.academy of sciences,beijing,china

In PartⅠthe authors have shown that heating sources in spring over the Tibetan Plateau(TP),and in particular the sensible heat flux(SHF),exhibit a significant weakening trend since the mid-1980s that is induced mainly by decreased surface wind *** possible reason of such a change is further investigated in PartⅡby analyzing historical observations and the NCEP/Department of Energy(DOE) *** steady declining trend in the surface wind speed over the TP after the 1970s arises mainly from the zonal *** the mean altitude of the TP is about 600 hPa and the surface flow is controlled by the East Asian subtropical westerly jet(EASWJ) for most parts of the year,the substantial tropospheric warming in the mid- and high latitudes to the north of the plateau results in a decrease of the meridional pressure gradient in the *** a result,the EASWJ and the surface winds over the TP are decelerated. Moreover,changes of the general circulation in the twentieth century simulated by 16 coupled climate models driven by natural and anthropogenic forcings are *** results suggest that sulfate aerosol indirect effects and ozone may be important in reproducing the weakening trend in EASWJ. Although nearly half of the models can successfully reproduce the observed trends in the EASWJ during the last two decades,there is an obvious spread in simulation of the spatial patterns of twentieth-century tropospheric temperatures,suggesting significant room still exists for improvement of the current state-of-theart coupled climate models.

关键词：

In situ Nd isotopic measurement of natural geological materials by LA-MC-ICPMS

在线全文

cnki会议

学校读者我要写书评

暂无评论

In situ Nd isotopic measurement of natural geological materi...

中国科学院地质与地球物理研究所2008学术年会

作者： YANG YueHeng,SUN JinFeng,XIE LieWen,FAN HongRui & wu FuYuan~+ state key {3. of Lithospheric Evolution,institute of Geology and Geophysics,chinese academy of sciences,beijing 100029, china

Using newly determined Sm isotopic abundances for correcting the isobaric interference of Sm on Nd and the established mass bias relationship between Sm and Nd,a series of in situ Nd isotopic measurements were conducted for relatively high Nd concentrations of natural geological materials, including apatite,titanite,monazite and perovskite on a Neptune multi-collector inductively coupled plasma mass spectrometry(MC-ICPMS),coupled to a 193.nm ArF excimer laser ablation *** results show that Ce has no significant influence on the precision and accuracy of Nd isotopic analyses for LREE-enriched geological minerals and that our approach is efficient in obtaining reliable Nd/Nd and Sm/Nd ratios for those materials with Sm/Nd<1(Sm/Nd<0.6).When combined with trace element and U-Pb isotope data,the in situ Nd isotopic data can provide important information on geological processes.

关键词： Nd isotope apatite titanite monazite perovskite LA-MC-ICPMS

Principal components of nuclear mass models

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science china(Physics,mechanics & Astronomy) 2024年第7期67卷 65-71页

作者： Xin-Hui wu Pengwei Zhao Department of Physics Fuzhou UniversityFuzhou 350108China state key laboratory of Nuclear Physics and Technology School of PhysicsPeking UniversityBeijing 100871China

Principal component analysis(PCA)is employed to extract the principal components(PCs)present in nuclear mass models for the first *** effects from different nuclear mass models are reintegrated and reorganized in the extracted *** PCs are recombined to build new mass models,which achieve better accuracy than the original theoretical mass *** comparison indicates that using the PCA approach,the effects contained in different mass models can be collaborated to improve nuclear mass predictions.

关键词： nuclear mass principal component analysis nuclear models statistical methods

维普期刊数据库

Drogue detection for autonomous aerial refueling via hybrid pigeon-inspired optimized color opponent and saliency aggregation

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Aeronautics 2024年第5期37卷 27-38页

作者： Tongyan wu Haibin DUAN Yanming FAN state key laboratory of Virtual Reality Technology and Systems School of Automation Science and Electrical EngineeringBeihang UniversityBeijing 100083China Virtual Reality Fundamental Research laboratory Department of Mathematics and TheoriesPeng Cheng LaboratoryShenzhen 518000China AVIC Shenyang Aircraft Design and Research institute Shenyang 110035China

Drogue detection is one of the challenging tasks in autonomous aerial refueling due to the requirement for accuracy and *** detection based on image intrinsic cues can achieve fast detection,but with poor *** studies reveal that optimization-based methods provide accurate and quick solutions for saliency *** paper presents a hybrid pigeon-inspired optimization method,the optimized color opponent,that aims to adjust the weight of color opponent channels to detect the drogue *** can optimize the weights in the selected aerial refueling scene offline,and the results are applied for drogue detection in the scene.A novel algorithm aggregated by the optimized color opponent and robust background detection is presented to provide better precision and *** results on benchmark datasets and aerial refueling images show that the proposed method successfully extracts the saliency region or drogue and exhibits superior performance against the other saliency detection methods with intrinsic *** algorithm designed in this paper is competent for the drogue detection task of autonomous aerial refueling.

关键词： Autonomous aerial refueling Drones Hybrid pigeon-inspired optimization Color opponent Saliency detection Saliency aggregation

维普期刊数据库

Flow instability of supercritical hydrocarbon fuel in a multi-channel cooling system

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Aeronautics 2024年第2期37卷 283-295页

作者： Yichao JIN Kun wu Xuejun FAN institute of Applied Physics and Computational Mathematics Beijing 100094China institute of mechanics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Thermally-induced flow instabilities are a critical issue in multi-channel regenerative cooling *** particular,the interactions between Density-Wave Oscillations(DWO)and Flow Maldistribution(FMD)can result in complex and disastrous instability *** study investigates the instability behaviors of hydrocarbon fluid in a four-channel system with a constant heat flux ratio using both frequency-and time-domain *** the heat flux increases,the in-tube flow sequentially destabilizes in each channel and converges to new equilibrium states,leading to the emergence of FMD *** also causes the system eigenvalue to change repeatedly from negative to positive rather than increasing ***,the system eigenvalues are between those of the two most unstable channels,indicating that the stability behavior of the entire system is dictated by the most unstable *** FMD occurs,flow oscillations are activated in channels with weak stability,and the in-tube flow is observed to evolve into various flow patterns,including stable flow,self-sustained oscillation,oscillation divergence,quasiperiodic oscillation,and oscillation *** novel instability mode of oscillation excursion involves a spontaneous transition of operating *** oscillates from an equilibrium state and then stabilizes at a new operational state after oscillation-induced ***,the newfound stable state may also be only temporary,with the in-tube flow regressing to the initial state,resulting in quasi-periodic oscillation.

关键词： Cooling Supercritical fluids Hydrocarbons Flow instability Flow maldistribution Density-wave oscillations

维普期刊数据库

In situ U-Pb dating of xenotime by laser ablation(LA)-ICP-MS

在线全文

学校读者我要写书评

暂无评论

In situ U-Pb dating of xenotime by laser ablation(LA)-ICP-MS

中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： LIU ZhiChao~(1,2),wu FuYuan~(1*),GUO ChunLi~3.ZHAO ZiFu~4,YANG JinHui~1 & SUN JinFeng~(1,2) 1 state key {3. of Litho spheric Evolution,institute of Geology and Geophysics,chinese academy of sciences,beijing 100029,china 2 Graduate University of chinese academy of sciences,beijing 100049,china 3.institute of Mineral Deposits,chinese academy of Geological sciences,beijing 10003.,china 4 School of Earth and Space sciences,University of Science and Technology of china,Hefei 23.026,china

Xenotime is an ideal mineral for U-Th-Pb isotopic dating because of its relatively high U and Th contents,but typically low concentration of common *** characteristics,and the fact that it is widespread throughout various types of rocks,suggest that the U-Th-Pb dating of xenotime has broad *** of U-Pb dating on xenotime by ion microprobe(such as SHPJMP) have increased in recent years,whereas studies by laser ablation(LA)-ICP-MS are still *** this study,we developed a technique for U-Pb dating of xenotime using the 193.nm ArF laser-ablation system and Agilent 7500a *** evaluate the reliability of our method,a xenotime standard,BS-1,was analyzed and calibrated against another xenotime standard,*** weighted mean Pb/U ages of 510.1±5.2 Ma(2a,n = 21),509.8±4.3.Ma(2 a,n = 21) and 510.0±4.6 Ma(2a,n = 21) were obtained using beam diameters of 16,24 and 3.μm,*** ages are identical to those determined by ID-TTMS method(weighted mean Pb/U age of 508.8±1.4 Ma),which supports the reliability of our LA-ICP-MS *** also analyzed xenotimes in leucogranites from South Tibet and granites from Xihuashan in southern china,and obtained accurate and precise ***,we observed systematic differences in Pb/U fractionation among xenotime,monazite and *** matrix-effect resulted in either under-correction or over-correction of fractionation,and thus led to inaccurate ***,a matrix -matched material is required for U-Pb dating of xenotime by LA-ICP-MS.

关键词： xenotime laser ablation(LA)-ICP-MS U-Pb dating

A buffer overflow detection and defense method based on RiSC-V instruction set extension

在线全文

cnki会议

学校读者我要写书评

暂无评论

Cybersecurity 2024年第2期7卷 28-43页

作者： Chang Liu Yan-Jun wu Jing-Zheng wu Chen Zhao Intelligent Software Research Center Institute of SoftwareChinese Academy of SciencesBejingChina University of chinese academy of sciences BeijingChina state key laboratory of Computer Science Institute of SoftwareChinese Academy of SciencesBeijingChina

Buffer overflow poses a serious threat to the memory security of modern operating *** overwrites the con-tents of other memory areas by breaking through the buffer capacity limit,destroys the system execution environ-ment,and provides implementation space for various system attacks such as program control flow *** makes it a wide range of harms.A variety of security technologies have been proposed to deal with system security problems including buffer *** example,No eXecute(NX for short)is a memory management technology commonly used in Harvard *** can refuse the execution of code which residing in a specific memory,and can effectively suppress the abnormal impact of buffer overflow on control ***,in recent years,it has also been used in the field of system security,deriving a series of solutions based on NX technology,such as ExecShield,DEP,StackGuard,***,these security solutions often rely too much on the processor archi-tecture so that the protection coverage is insufficient and the accuracy is *** in the emerging system architecture field represented by RiSC-V,there is still a lack of effective solutions for buffer overflow *** the continuous rapid development of the system architecture,it is urgent to develop defense methods that are applicable to different system application environments and oriented to all executable memory spaces to meet the needs of system security ***,we propose BOP,A new system memory security design method based on RISC-V extended instructions,to build a RISC-V buffer overflow detection and defense system and deal with the buffer overflow threat in *** to this method,NX technology can be combined with program control flow analysis,and Nx bit mechanism can be used to manage the executability of memory space,so as to achieve a more granular detection and defense of buffer overflow attacks that may occur in RISC-V system

关键词： RISc-V Operating system security Buffer overflow Control flow hijacking Nx bit Xibop

Improve chinese Aspect Sentiment Quadruplet Prediction via Instruction Learning Based on Large Generate Models

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第3期78卷 3391-3412页

作者： Zhaoliang wu Yuewei wu Xiaoli Feng Jiajun Zou Fulian Yin College of Information and Communication Engineering Communication University of ChinaBeijing100024China The state key laboratory of Media Convergence and Communication Communication University of ChinaBeijing100024China Department of Electronic Engineering Tsinghua UniversityBeijing100084China

Aspect-Based Sentiment Analysis(ABSA)is a fundamental area of research in Natural Language Processing(NLP).Within ABSA,Aspect Sentiment Quad Prediction(ASQP)aims to accurately identify sentiment quadruplets in target sentences,including aspect terms,aspect categories,corresponding opinion terms,and sentiment ***,most existing research has focused on English ***,while ASQP has seen significant progress in English,the chinese ASQP task has remained relatively *** inspiration from methods applied to English ASQP,we propose chinese generation templates and employ prompt-based instruction learning to enhance the model’s understanding of the task,ultimately improving ASQP performance in the chinese ***,under the same pre-training model configuration,our approach achieved a 5.79%improvement in the F1 score compared to the previously leading ***,when utilizing a larger model with reduced training parameters,the F1 score demonstrated an 8.14%***,we suggest a novel evaluation metric based on the characteristics of generative models,better-reflecting model *** results validate the effectiveness of our approach.

关键词： ABSA ASQP LLMs sentiment analysis chinese comments