期刊文献+
共找到486篇文章
< 1 2 25 >
每页显示 20 50 100
Analysis of level structure and monopole effects in Ca isotopes
1
作者 Jin Li Ai-Xi Chen +1 位作者 Amir Jalili Han-Kui Wang 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第10期161-167,共7页
Understanding the properties of nuclei near the double magic nucleus^(40)Ca is crucial for both nuclear theory and experiments.In this study,Ca isotopes were investigated using an extended pairing-plus-quadrupole mode... Understanding the properties of nuclei near the double magic nucleus^(40)Ca is crucial for both nuclear theory and experiments.In this study,Ca isotopes were investigated using an extended pairing-plus-quadrupole model with monopole corrections.The negative-parity states of^(44)Ca were coupled with the intruder orbital g_(9/2)at 4 MeV.The values of E_(4+)/E_(2+)agree well with experimental trend from^(42)Ca to^(50)Ca,considering monopole effects between νf_(7/2)and νp_(3/2)(νf_(5/2)).This monopole effect,determined from data of^(48)Ca and^(50)Ca,supports the proposed new nuclear magic number N=34 by predicting a high-energy 2^(+)state in^(54)Ca. 展开更多
关键词 Shell model Doubly magic ISOTOPES Monopole effects level structure
下载PDF
A DESIGN OF THREE-DIMENSIONAL SPATIAL DATA MODEL AND ITS DATA STRUCTURE IN GEOLOGICAL EXPLORATION ENGINEERING
2
作者 Cheng Penggen Gong Jianya +1 位作者 Wang Yandong Sui Haigang 《Geo-Spatial Information Science》 1999年第1期78-85,共8页
The key to develop 3-D GISs is the study on 3-D data model and data structure. Some of the data models and data structures have been presented by scholars. Because of the complexity of 3-D spatial phenomenon, there ar... The key to develop 3-D GISs is the study on 3-D data model and data structure. Some of the data models and data structures have been presented by scholars. Because of the complexity of 3-D spatial phenomenon, there are no perfect data structures that can describe all spatial entities. Every data structure has its own advantages and disadvantages. It is difficult to design a single data structure to meet different needs. The important subject in the3-D data models is developing a data model that has integrated vector and raster data structures. A special 3-D spatial data model based on distributing features of spatial entities should be designed. We took the geological exploration engineering as the research background and designed an integrated data model whose data structures integrats vector and raster data byadopting object-oriented technique. Research achievements are presented in this paper. 展开更多
关键词 GEOLOGICAL EXPLORATION ENGINEERING GEOGRAPHIC information system three DIMENSIONAL DATA model DATA structure
下载PDF
Investigation of the level spectra of nuclei in the northeast region of doubly magic^(40)Ca with intruder orbit g_(9/2) 被引量:2
3
作者 Jin-Zhong Han Shuai Xu +1 位作者 Amir Jalili Han-Kui Wang 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2023年第6期115-123,共9页
This study utilizes large-scale shell model calculations with the extended pairing and multipole–multipole force model(EPQQM)to investigate low-lying states in the nuclei of^(42)Ca,^(42)Sc,and^(42−44)Ti.The model spa... This study utilizes large-scale shell model calculations with the extended pairing and multipole–multipole force model(EPQQM)to investigate low-lying states in the nuclei of^(42)Ca,^(42)Sc,and^(42−44)Ti.The model space in this study includes the fp shell as well as the intruder g_(9/2)orbit,which accurately reproduces the positive parity levels observed in the aforementioned nuclei and predicts high energy states with negative parity coupled with the intruder g_(9/2).The study further predicts two different configurations in^(43)Ti at around 6 MeV,specificallyπf_(7/2)^(2)νg_(9/2)andπf_(7/2)g_(9/2)νf_(7/2),both of which involve the intruder orbit g_(9/2).The levels coupled with the intruder g_(9/2)in^(44)Ti are predicted to lie between 7 and 11 MeV.The inclusion of the intruder orbit g_(9/2)is crucial for the exploration of high energy states in the northeast region of the doubly magic nucleus^(40)Ca. 展开更多
关键词 Shell model Doubly magic level structure
下载PDF
Application of 3D Static Modelling in Reservoir Characterization:A Case Study from the Qishn Formation in Sharyoof Oil Field,Masila Basin,Yemen 被引量:1
4
作者 Emad A.ABDULLAH Ahmed ABDELMAKSOUD Musab A.HASSAN 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2022年第1期348-368,共21页
Three-dimensional(3 D)static modelling techniques are applied to the characterization of the Qishn Formation(Fm.)in the Sharyoof oil field locating within the Masila basin,southeastern Yemen.The present study was init... Three-dimensional(3 D)static modelling techniques are applied to the characterization of the Qishn Formation(Fm.)in the Sharyoof oil field locating within the Masila basin,southeastern Yemen.The present study was initiated by the seismic structural interpretation,followed by building a 3 D structural framework,in addition to analysing well log data and from these,3 D facies and petrophysical models are constructed.In the Sharyoof oil field,the Qishn Fm.exhibits depth values within the range of 400-780 m below sea level,with a general increase towards the SSE.A set of high dip angle normal faults with a general ENE-WSW trend dissect the rocks.The strata are also folded as a main anticline with an axis that is parallel to the fault trend,formed as a result of basement uplift.According to the facies models,the Qishn Fm.comprises 43.83% limestone,21.53% shale,21.26% sandstone,13.21% siltstone and 0.17% dolomite.The Qishn Carbonates Member has low porosity values making it a potential seal for the underlying reservoirs whereas the Upper Qishn Clastics SI A and C have good reservoir quality and SIB has fair reservoir quality.The Upper Qishn Clastics S2 and S3 also have fair reservoir quality,while the Lower Qishn Clastics zone has good reservoir quality.The water saturation decreases towards the west and east and increases towards north and south.The total original oil in-place(OOIP)of the Upper Qishn clastics is 106 million STB within the SI A,SIC and S2 zones.Drilling of development wells is recommended in the eastern study area,where good trapping configuration is exhibited in addition to the presence of a potential seal(Upper Qishn Carbonates Member)and reservoir(Qishn Clastics Member)with high porosity and low water saturation. 展开更多
关键词 upstream exploration petroleum basins seismic interpretation structural modelling well log analysis facies modelling petrophysical modelling Sayun-Masila basin
下载PDF
A Multilevel Secure Relation-Hierarchical Data Model for a Secure DBMS
5
作者 朱虹 冯玉才 《Journal of Modern Transportation》 2001年第1期8-16,共9页
A multilevel secure relation hierarchical data model for multilevel secure database is extended from the relation hierarchical data model in single level environment in this paper. Based on the model, an upper lowe... A multilevel secure relation hierarchical data model for multilevel secure database is extended from the relation hierarchical data model in single level environment in this paper. Based on the model, an upper lower layer relationalintegrity is presented after we analyze and eliminate the covert channels caused by the database integrity.Two SQL statements are extended to process polyinstantiation in the multilevel secure environment.The system based on the multilevel secure relation hierarchical data model is capable of integratively storing and manipulating complicated objects ( e.g. , multilevel spatial data) and conventional data ( e.g. , integer, real number and character string) in multilevel secure database. 展开更多
关键词 DATABASES data structure data models secure DBMS covert channels mandatory access control POLYINSTANTIATION hierarchical classification non hierarchical category security level integrity cluster index
下载PDF
Effects of Multicollinearity on Type I Error of Some Methods of Detecting Heteroscedasticity in Linear Regression Model
6
作者 Olusegun Olatayo Alabi Kayode Ayinde +2 位作者 Omowumi Esther Babalola Hamidu Abimbola Bello Edward Charles Okon 《Open Journal of Statistics》 2020年第4期664-677,共14页
Heteroscedasticity and multicollinearity are serious problems when they exist in econometrics data. These problems exist as a result of violating the assumptions of equal variance between the error terms and that of i... Heteroscedasticity and multicollinearity are serious problems when they exist in econometrics data. These problems exist as a result of violating the assumptions of equal variance between the error terms and that of independence between the explanatory variables of the model. With these assumption violations, Ordinary Least Square Estimator</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">(OLS) will not give best linear unbiased, efficient and consistent estimator. In practice, there are several structures of heteroscedasticity and several methods of heteroscedasticity detection. For better estimation result, best heteroscedasticity detection methods must be determined for any structure of heteroscedasticity in the presence of multicollinearity between the explanatory variables of the model. In this paper we examine the effects of multicollinearity on type I error rates of some methods of heteroscedasticity detection in linear regression model in other to determine the best method of heteroscedasticity detection to use when both problems exist in the model. Nine heteroscedasticity detection methods were considered with seven heteroscedasticity structures. Simulation study was done via a Monte Carlo experiment on a multiple linear regression model with 3 explanatory variables. This experiment was conducted 1000 times with linear model parameters of </span><span style="white-space:nowrap;"><em><span style="font-family:Verdana;">β</span></em><sub><span style="font-family:Verdana;">0</span></sub><span style="font-family:Verdana;"> = 4 , </span><em><span style="font-family:Verdana;">β</span></em><sub><span style="font-family:Verdana;">1</span></sub><span style="font-family:Verdana;"> = 0.4 , </span><em><span style="font-family:Verdana;">β</span></em><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">= 1.5</span></span></span><span style="font-family:""><span style="font-family:Verdana;"> and </span><em style="font-family:""><span style="font-family:Verdana;">β</span><span style="font-family:Verdana;"><sub>3 </sub></span></em><span style="font-family:Verdana;">= 3.6</span><span style="font-family:Verdana;">. </span><span style="font-family:Verdana;">Five (5) </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">levels of</span><span style="white-space:nowrap;font-family:Verdana;"> </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">mulicollinearity </span></span><span style="font-family:Verdana;">are </span><span style="font-family:Verdana;">with seven</span><span style="font-family:""> </span><span style="font-family:Verdana;">(7) different sample sizes. The method’s performances were compared with the aids of set confidence interval (C.I</span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;">) criterion. Results showed that whenever multicollinearity exists in the model with any forms of heteroscedasticity structures, Breusch-Godfrey (BG) test is the best method to determine the existence of heteroscedasticity at all chosen levels of significance. 展开更多
关键词 Regression model Heteroscedasticity Methods Heteroscedasticity structures MULTICOLLINEARITY Monte Carlo Study Significance levels Type I Error Rates
下载PDF
The effects of population aging on industrial structure upgrading:Empirical analysis of provincial and threshold characteristics in China
7
作者 Mao Hu Linyu Xiao Hong Qiu 《Chinese Journal of Population,Resources and Environment》 2024年第3期356-366,共11页
Global population aging trends are intensifying,presenting multifaceted economic and social challenges for countries worldwide.As the world’s largest developing country,China has entered a phase of extreme demographi... Global population aging trends are intensifying,presenting multifaceted economic and social challenges for countries worldwide.As the world’s largest developing country,China has entered a phase of extreme demographic aging,posing significant questions about its impact on the ongoing upgrading of industrial structures.How does this demographic shift influence the upgrading of industrial structures,and does technological innovation mitigate or exacerbate this impact?The empirical results indicate that population aging impedes upgrading the industrial structure,while technological innovation positively affects the relationship between the two.Moreover,using technological innovation as a threshold variable,the impact of population aging on industrial structure upgrading evolves in a“gradient”manner from“impediment”to“insignificant”to“promotion”as the technological innovation levels increase.These findings offer practical guidance for tailoring industrial policies to different stages of technological advancement. 展开更多
关键词 Population aging Technological innovation level Industrial structure upgrading Panel threshold models Instrumental variable method
下载PDF
Change in self-image pressure level before and after autologous fat breast augmentation and its effect on social adaptability
8
作者 Jian Li Hui-Min Wang +2 位作者 Yang Jiang Zhen-Nan Liu Bai-Hui He 《World Journal of Psychiatry》 SCIE 2024年第6期920-929,共10页
BACKGROUND There is an increasingly strong demand for appearance and physical beauty in social life,marriage,and other aspects with the development of society and the improvement of material living standards.An increa... BACKGROUND There is an increasingly strong demand for appearance and physical beauty in social life,marriage,and other aspects with the development of society and the improvement of material living standards.An increasing number of people have improved their appearance and physical shape through aesthetic plastic surgery.The female breast plays a significant role in physical beauty,and droopy or atrophied breasts can frequently lead to psychological inferiority and lack of confidence in women.This,in turn,can affect their mental health and quality of life.AIM To analyze preoperative and postoperative self-image pressure-level changes of autologous fat breast augmentation patients and their impact on social adaptability.METHODS We selected 160 patients who underwent autologous fat breast augmentation at the First Affiliated Hospital of Xinxiang Medical University from January 2020 to December 2022 using random sampling method.The general information,selfimage pressure level,and social adaptability of the patients were investigated using a basic information survey,body image self-assessment scale,and social adaptability scale.The self-image pressure-level changes and their effects on the social adaptability of patients before and after autologous fat breast augmentation were analyzed.RESULTS We collected 142 valid questionnaires.The single-factor analysis results showed no statistically significant difference in the self-image pressure level and social adaptability score of patients with different ages,marital status,and monthly income.However,there were significant differences in social adaptability among patients with different education levels and employment statuses.The correlation analysis results revealed a significant correlation between the self-image pressure level and social adaptability score before and after surgery.Multiple factors analysis results showed that the degree of concern caused by appearance in selfimage pressure,the degree of possible behavioral intervention,the related distress caused by body image,and the influence of body image on social life influenced the social adaptability of autologous fat breast augmentation patients.CONCLUSION The self-image pressure on autologous fat breast augmentation patients is inversely proportional to their social adaptability. 展开更多
关键词 Autologous fat breast augmentation surgery Self-image stress level Social adaptability Analysis of correlation Structural equation model
下载PDF
Storyline Extraction of Document-Level Events Using Large Language Models
9
作者 Ziyang Hu Yaxiong Li 《Journal of Computer and Communications》 2024年第11期162-172,共11页
This article proposes a document-level prompt learning approach using LLMs to extract the timeline-based storyline. Through verification tests on datasets such as ESCv1.2 and Timeline17, the results show that the prom... This article proposes a document-level prompt learning approach using LLMs to extract the timeline-based storyline. Through verification tests on datasets such as ESCv1.2 and Timeline17, the results show that the prompt + one-shot learning proposed in this article works well. Meanwhile, our research findings indicate that although timeline-based storyline extraction has shown promising prospects in the practical applications of LLMs, it is still a complex natural language processing task that requires further research. 展开更多
关键词 Document-level Storyline Extraction Timeline Large Language models Topological Structure of Storyline Prompt Learning
下载PDF
Contour tracking using weighted structure tensor based variational level set
10
作者 胡宏伟 马波 曹淑娟 《Journal of Beijing Institute of Technology》 EI CAS 2014年第2期218-225,共8页
A novel contour tracking method using weighted structure tensor based variational level set is proposed in this paper.The image is first converted to weighted structure tensor field by extracting apositive definite sy... A novel contour tracking method using weighted structure tensor based variational level set is proposed in this paper.The image is first converted to weighted structure tensor field by extracting apositive definite symmetric covariance matrix for each pixel.Then,a level set method is employed to represent object contour implicitly which separates the image domain into two areas each modeled by tensor field based Gaussian mixture model separately.By solving agradient flow equation of energy functional with respect to the level set,the object contour will converge to its real profile in the newly arrived frame.Experimental results on several video sequences demonstrate the better performance of our method than the other two contour tracking algorithms. 展开更多
关键词 contour tracking weighted structure tensor Gaussian mixture model level set
下载PDF
Model Design for AMT Data Inversion
11
作者 Shancong Yao Ruliang Zhang +2 位作者 Baoqiang Qiao Hanping Wan Xiang Yu 《Open Journal of Geology》 2017年第3期420-428,共9页
By analyzing the characters of the mainstream commercial magnetotelluric inversion softwares in dealing with audio magnetotelluric data, a dynamic model-making method for inversion has been developed based on the obse... By analyzing the characters of the mainstream commercial magnetotelluric inversion softwares in dealing with audio magnetotelluric data, a dynamic model-making method for inversion has been developed based on the observed AMT data. This method focusing on model domain can adjust mesh’s scale and model’s dimension depending on the field data just with a few parameters. By this, it is convenient to study the geo-electrical anomalies variations of different scale or dimensional models. Applying such model-making technique into the known hardrock geological setting, it is easy to obtain a new geo-electrical model which agrees with the resistivity curves of core samples better than before. It is demonstrated that this can increase the recognition of the resistivity contrast and deserves studying further. 展开更多
关键词 AMT EXPLORATION Making-model Based on AMT Data Geo-Electric STRUCTURE
下载PDF
基于DEMATEL-AISM的铁路工程建设风险识别影响因素与优化策略研究 被引量:6
12
作者 郭峰 李媛媛 +1 位作者 彭晓菁 古江林 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第2期802-811,共10页
铁路工程建设大型化、复杂化和系统化的发展趋势下,潜在的风险因素日益繁多,铁路工程建设高质量和可持续发展之路充满挑战。风险识别作为风险管理的首要环节,是应对和控制铁路工程建设风险的关键,受到项目内外部多方面因素的影响,且现... 铁路工程建设大型化、复杂化和系统化的发展趋势下,潜在的风险因素日益繁多,铁路工程建设高质量和可持续发展之路充满挑战。风险识别作为风险管理的首要环节,是应对和控制铁路工程建设风险的关键,受到项目内外部多方面因素的影响,且现有实践中没有系统的指导,导致风险识别工作易存在疏漏。基于此,通过文献研究和因子分析,提取铁路工程建设风险识别的核心影响因素,运用决策与试验评价实验室和解释结构模型的方法,构建对抗多级递阶结构模型(DEMATEL-AISM),计算铁路工程建设风险识别各影响因素的重要程度及其耦合关系。研究结果表明:铁路工程建设风险识别的效果受到直接层、间接层和根源层3层因素共同作用,其中,危险源监测分析、人员风险意识、风险调查措施、风险应对能力、铁路建设目标、预期风险后果和风险识别技术是影响风险识别结果的关键因素,在铁路工程建设风险管理工作的开展中应重点关注和控制。基于模型结果,分析风险识别影响因素的层级结构及因果关系,并从风险内部控制、项目一体化风险管理体系构建和动态风险预警机制设立3个方面,提出了铁路工程建设风险识别的建议和策略。研究结果有助于提高大型铁路工程建设风险辨识结果的全面性和科学性,对构建铁路工程建设风险识别体系具有一定参考价值和借鉴意义。 展开更多
关键词 铁路工程建设 风险辨识 风险识别影响因素 对抗多级递阶结构模型(DEMATEL-AISM)
下载PDF
水位差法模拟波浪荷载作用下大直径圆筒稳定性离心模型试验研究
13
作者 任国峰 关云飞 +2 位作者 周春儿 顾行文 徐光明 《岩土工程学报》 EI CAS CSCD 北大核心 2024年第S01期27-31,共5页
某人工岛护岸工程采用大直径圆筒结构,结构直径和高度尺寸较大,工程所处位置波浪条件恶劣。采用水位差法等效模拟波浪荷载,开展波浪荷载作用下大圆筒施工期稳定特性离心模型试验研究,结果表明,在25 a一遇波吸力荷载作用下,筒体位移模式... 某人工岛护岸工程采用大直径圆筒结构,结构直径和高度尺寸较大,工程所处位置波浪条件恶劣。采用水位差法等效模拟波浪荷载,开展波浪荷载作用下大圆筒施工期稳定特性离心模型试验研究,结果表明,在25 a一遇波吸力荷载作用下,筒体位移模式近似平移,侧向位移量约353 mm,筒顶沉降约为187 mm,施工阶段钢圆筒整体稳定;筒壁环向拉应力均值约为90 MPa,处于钢圆筒材料允许应力范围内;筒壁海侧土压力值随水位差增大至峰值后趋于稳定,表明筒体与周围邻近土体之间没有新的相对位移趋势,大直径钢圆筒护岸结构在波浪荷载作用下是稳定安全的。 展开更多
关键词 大直径圆筒结构 水位差法 离心模型试验 机理 稳定性
下载PDF
河南银洞坡金矿“三位一体”找矿预测地质模型及应用示范
14
作者 唐相伟 张晓飞 +3 位作者 杨泽强 郭跃闪 王海生 李积山 《地质通报》 CAS CSCD 北大核心 2024年第7期1120-1132,共13页
河南银洞坡金矿位于河南省桐柏县朱庄镇,为一特大型金矿床,同体共生银、铅锌。运用勘查区找矿预测方法与理论,构建成矿地质体、成矿构造与成矿结构面和成矿作用特征标志为主的“三位一体”找矿预测地质模型。野外调查和矿床学研究认为,... 河南银洞坡金矿位于河南省桐柏县朱庄镇,为一特大型金矿床,同体共生银、铅锌。运用勘查区找矿预测方法与理论,构建成矿地质体、成矿构造与成矿结构面和成矿作用特征标志为主的“三位一体”找矿预测地质模型。野外调查和矿床学研究认为,矿床成因为与早白垩世岩浆作用有关的中低温岩浆热液矿床,主成矿阶段温度介于200~350℃之间,碳、氢、氧、硫同位素研究表明,成矿物质和成矿流体主要来源于岩浆。确定成矿地质体为矿区深部隐伏早白垩世花岗岩体;成矿结构面为岩性界面(硅/钙面)、褶皱成矿构造系统结构面、沉积成岩结构面;成矿作用特征标志主要为矽卡岩化、钾化、黄铁绢英岩化、硅化、铁白云石化、萤石矿化、碳酸盐化。由此建立了银洞坡金矿找矿预测地质模型,圈定了找矿靶区,施工的钻孔见矿率达到85%,对该地区及邻区进一步找矿具有现实的指导意义。 展开更多
关键词 找矿突破 找矿预测模型 成矿地质体 成矿结构面 成矿作用特征标志 银洞坡金矿 矿产勘查工程
下载PDF
油气地质勘探将从烃源岩时代进入幔源油气新时代
15
作者 林隆栋 袁学诚 李玉琪 《西安石油大学学报(社会科学版)》 2024年第2期70-77,共8页
简要梳理了人类石油勘探发展历程,分析并研究了国内外25个油田(或盆地、油区)的勘探资料,得出结论:石油地质勘探经历过的第一个阶段是背斜(构造)勘探阶段(19世纪60年代~20世纪60年代),第二个阶段是烃源岩勘探阶段(20世纪30年代至今),现... 简要梳理了人类石油勘探发展历程,分析并研究了国内外25个油田(或盆地、油区)的勘探资料,得出结论:石油地质勘探经历过的第一个阶段是背斜(构造)勘探阶段(19世纪60年代~20世纪60年代),第二个阶段是烃源岩勘探阶段(20世纪30年代至今),现在已经进入一个全新的阶段——幔源油气勘探时代。依据幔源油气理论,提出了创新的“盆-壳-幔镜像叠置成藏模式”。 展开更多
关键词 背斜(构造)勘探 烃源岩勘探 幔源油气理论及勘探 盆-壳-幔镜像叠置成藏模式
下载PDF
西非北部被动陆缘盆地油气地质特征与勘探方向
16
作者 田纳新 王大鹏 +1 位作者 郑求根 杨光庆 《中国地质调查》 CAS 2024年第2期17-27,共11页
西非北部盆地勘探程度较低,但资源潜力巨大。基于板块构造理论,通过结合地震与地质方法的综合研究,分析了西非北部主要地质时期的原型盆地,对比了各盆地的结构特征及其沉积充填差异性,解剖已发现油气藏,建立成藏模式,指出下一步勘探方... 西非北部盆地勘探程度较低,但资源潜力巨大。基于板块构造理论,通过结合地震与地质方法的综合研究,分析了西非北部主要地质时期的原型盆地,对比了各盆地的结构特征及其沉积充填差异性,解剖已发现油气藏,建立成藏模式,指出下一步勘探方向。研究发现:西非北部被动陆缘盆地群经历了前寒武纪—二叠纪前裂陷、三叠纪—早侏罗世裂陷和中侏罗世至今的陆缘3个演化阶段,形成了断陷型、断坳型和坳陷型3个被动陆缘盆地亚类。断陷型盆地形成单源-构造型成藏模式,勘探目标以裂谷层系的构造成藏组合为主;断坳型盆地可形成双源-双组合型成藏模式,大陆架上的缓坡带以裂谷层系构造圈闭为主,在台地边缘应寻找礁体和内幕岩溶,陡坡带上部的主要勘探目标应为规模较大的滑动-滑塌形成的斜坡扇,下部应关注成熟烃源岩层系内扇体所形成的上白垩统和下白垩统砂岩构造-岩性圈闭;坳陷型盆地以坳陷层系烃源岩为主,主要勘探对象为陡坡下部的浊积砂岩及台地缓坡三角洲砂体,台地边缘礁滩体、台地碳酸盐岩风化壳岩溶和断裂带岩溶也是值得重视的勘探方向。研究可为勘探程度低、资料获取难的被动陆缘深水油气勘探选区评价提供借鉴。 展开更多
关键词 西非北部 盆地结构 成藏模式 勘探方向 被动陆缘盆地
下载PDF
基于结构主题模型的民航管制不安全事件主题识别
17
作者 张洪海 石宗北 +2 位作者 李一可 周锦伦 王雨菲 《中国安全生产科学技术》 CAS CSCD 北大核心 2024年第11期163-169,共7页
为探究民航管制运行不安全事件的发生规律及特点,采用结构主题模型捕捉报告中的词汇共现及层次结构。考虑结构主题的语义连贯性以及排他性等指标,辨识管制运行事件的最优主题数目。选取事件严重度及发生时间等协变量,构建融合多变量的... 为探究民航管制运行不安全事件的发生规律及特点,采用结构主题模型捕捉报告中的词汇共现及层次结构。考虑结构主题的语义连贯性以及排他性等指标,辨识管制运行事件的最优主题数目。选取事件严重度及发生时间等协变量,构建融合多变量的主题分析,挖掘不同类型事件的严重度差异性及在时间维度上的演化趋势。最后,基于航空安全自愿报告系统2018-2022年的4346起管制事件报告进行实证分析。研究结果表明:与管制运行有关的不安全事件可分为管制移交、恶劣天气、人为因素事件、夜航航班、场面滑行、起飞离场、部门协调、雷达间隔、设备故障、进近程序、陆空对话、复杂空域环境、飞行冲突、飞行高度、冲/偏出跑道及跑道侵入15类;飞行区滑行、进近程序、飞行冲突等事件更易产生严重事故;飞行高度有关的不安全事件呈逐年上升趋势。研究结果可为提升管制运行安全风险水平提供理论支持,并为管理人员针对性施策提供参考。 展开更多
关键词 空中交通管理 民航管制运行 安全水平 不安全事件 结构主题模型
下载PDF
县域城镇化背景下关中平原城市群近郊农民外出行为决策机理研究
18
作者 刘晓君 张海涛 《小城镇建设》 2024年第11期31-38,86,共9页
研究县域城镇化背景下农民外出行为决策机理,是有效引导农业人口就地就近转移、缓解“大城市病”、促进城乡融合发展的重要基础工作。本文基于城乡人口流动视角,依据推拉理论和计划行为理论构建农民外出行为决策机理模型,采集关中平原... 研究县域城镇化背景下农民外出行为决策机理,是有效引导农业人口就地就近转移、缓解“大城市病”、促进城乡融合发展的重要基础工作。本文基于城乡人口流动视角,依据推拉理论和计划行为理论构建农民外出行为决策机理模型,采集关中平原城市群近郊农村调研问卷362份,运用结构方程模型实证了该地区农民外出行为决策机理。结果表明:1)感知推力、感知拉力、感知核力通过影响农民外出行为态度及意愿间接作用于外出实际行为。其中,感知推力和感知拉力为正向影响,感知核力为负向影响。2)农民的感知个人能力和感知家庭能力在外出行为意愿与外出实际行为之间具有显著的调节作用,且感知个人能力的调节作用更强。最后,基于决策机理探讨了县域城镇化政策含义并提出了提升村容村貌减弱农村推力作用、盘活闲置资产巩固农村核力优势、丰富乡镇经济业态增强乡镇拉力作用、多途径多渠道提升农民县城生活品质等对策建议。 展开更多
关键词 县域城镇化 农民外出行为 结构方程模型 决策机理 调节作用
下载PDF
层冰作用下直立圆柱结构冰载荷研究
19
作者 余朝歌 田于逵 +3 位作者 刚旭皓 孔帅 季少鹏 王迎晖 《船舶力学》 EI CSCD 北大核心 2024年第2期169-178,共10页
层冰是冰区海工结构作业时遭遇的主要冰况之一,直立结构是海工结构的常见构型,因此,开展层冰作用下直立结构冰载荷研究对海工结构抗冰强化设计和安全评估具有重要意义。本文首先对层冰与直立结构作用过程进行概括分析。然后开展直立圆... 层冰是冰区海工结构作业时遭遇的主要冰况之一,直立结构是海工结构的常见构型,因此,开展层冰作用下直立结构冰载荷研究对海工结构抗冰强化设计和安全评估具有重要意义。本文首先对层冰与直立结构作用过程进行概括分析。然后开展直立圆柱结构冰载荷的机理性试验,研究层冰的失效行为以及结构冰载荷的特征。最后基于黏聚单元模型和海冰软化本构开发层冰与结构作用模拟的数值仿真模型,对层冰的裂纹扩展和破碎过程进行模拟,同时利用试验数据对数值仿真模型的正确性进行验证。本研究工作可为结构冰载荷的数值和试验研究奠定重要基础,为冰区海工结构的设计建造提供技术参考。 展开更多
关键词 层冰 直立结构 冰载荷 模型试验 黏聚单元模型
下载PDF
基于粘聚力单元的平整冰与海洋桩柱结构相互作用机理研究
20
作者 俞同强 刘昆 +1 位作者 刘俊杰 王自力 《船舶力学》 EI CSCD 北大核心 2024年第1期115-128,共14页
平整冰与海洋桩柱结构的相互作用问题十分复杂,往往涉及到海冰的破碎、失效和堆积等现象。平整冰破坏问题本质上是一个材料脆性破坏的问题,然而传统有限元方法的单元失效机制在处理该问题时有着很大的局限性,不能合理反映平整冰破碎后... 平整冰与海洋桩柱结构的相互作用问题十分复杂,往往涉及到海冰的破碎、失效和堆积等现象。平整冰破坏问题本质上是一个材料脆性破坏的问题,然而传统有限元方法的单元失效机制在处理该问题时有着很大的局限性,不能合理反映平整冰破碎后碎冰的变形和运动状态。因此,有必要发展现有仿真技术,建立合理的模型化方法来解决平整冰破坏相关关键问题。本文通过自定义海冰材料本构模拟海冰材料力学特性,并通过粘聚力单元模拟平整冰破坏时裂纹的产生和扩展,通过开展海洋桩柱结构与平整冰相互作用的仿真分析,分析平整冰在受桩柱作用时的破坏失效模式及两者的相互作用载荷,并与相关模型试验比较验证本文所提出方法的可靠性。研究表明,本文所采用的方法能够有效模拟平整冰在受桩柱作用时的挤压和弯曲破坏,同时能够较为准确地预报冰载荷。研究成果对于海洋桩柱结构冰载荷的预报和结构的设计具有重要的参考意义。 展开更多
关键词 平整冰 海洋桩柱 海冰材料本构 粘聚力单元 破坏失效模式 数值仿真
下载PDF
上一页 1 2 25 下一页 到第
使用帮助 返回顶部