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Seedling potential of trees species along the elevational gradient in temperate hill forest of central Nepal
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作者 DANI Ram Sharan BANIYA Chitra Bahadur 《Journal of Mountain Science》 SCIE CSCD 2024年第4期1329-1344,共16页
Regeneration status of tree species along elevation gradient in temperate hill forest was not understood greatly.Present research examined the tree diversity and its regeneration patterns along an elevation gradient i... Regeneration status of tree species along elevation gradient in temperate hill forest was not understood greatly.Present research examined the tree diversity and its regeneration patterns along an elevation gradient in temperate hill forest,central Nepal.Data were collected from 300 sample plots within vertical elevation bands of 10,ranging from 1365 to 2450 m asl.A random sampling method was used for data collection in three seasons,winter,pre-monsoon and post monsoon seasons.Diameter at breast height(DBH)was used to broadly categorize the plant individual into trees,saplings and seedlings.The tree species richness ranged from 12 to 25 with density of 350 to 1200 individuals per hectare.Species richness of tree and sapling showed statistically significant unimodal pattern,which peaked at mid-elevation.Elevation showed a strong and positive linear correlation with the seedling density(Deviance=0.99,p<0.001)and a significant hump-shaped relationship with sapling density(Deviance=0.95,p<0.001).Similarly,elevations showed a statistically significant negative hump-shaped relationship with all trees,saplings and seedling stages(Deviances=0.89,0.87 and 0.57).The highest values of the Shannon-Wiener index and the lowest value of the Simpson index were found at mid-elevation for all growth forms.Nearly 92%of tree species were found at regenerating stage;49%in a good renewal regeneration status,32%in fair renewal regeneration,and 11%at a poor regenerating condition.Nevertheless,4%of tree species were reported as non-regenerating stages and 4%were newly introduced species.Hence,the regeneration status of the study area was considered fairly well since sapling(78.5%)>seedling(10.6%)≤mature(10.9%).Among tested environmental variables,elevation and annual mean rainfall were the most influential factors in the regeneration of tree species. 展开更多
关键词 Regeneration potential Chandragiri hill Altitudinal gradient Species diversity Tree species richness
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基于Hill分级建立胃食管阀瓣功能自动评估的人工智能辅助系统
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作者 王甘红 夏开建 +2 位作者 周燕婷 陈健 徐璐 《中国医疗设备》 2024年第11期17-26,共10页
目的利用深度学习技术开发基于Hill分级的人工智能模型,提升内镜医师对食管胃连接部形态的分类效率和准确性。方法本研究采集了4个数据集,包括总计1143张胃食管瓣膜(Gastroesophageal Flap Valve,GEFV)图像和17个胃镜视频,涵盖HillⅠ、... 目的利用深度学习技术开发基于Hill分级的人工智能模型,提升内镜医师对食管胃连接部形态的分类效率和准确性。方法本研究采集了4个数据集,包括总计1143张胃食管瓣膜(Gastroesophageal Flap Valve,GEFV)图像和17个胃镜视频,涵盖HillⅠ、Ⅱ、Ⅲ、Ⅳ级的GEFV图像。图像经过预处理和增强,利用基于卷积神经网络(Convolutional Neural Network,CNN)和Transformer架构的预训练模型进行迁移学习。评估模型性能时,考量准确度、精准度、召回率、F1得分等指标,并将其与内镜医师在不同阈值下的预测准确性进行对比。为增强模型透明度,采用多种可解释性分析技术,包括t-SNE、梯度加权分类激活映射(Grad-CAM)和SHAP技术。最终,模型被转化为开放神经网络交换(ONNX)格式,并部署到多种设备终端上,以实现GEFV形态的实时Hill分级。结果EfficientNet-Hill模型的性能表现超越了其他6种CNN和Transformer模型,在外部测试集上的准确度达83.32%,略低于高级内镜医师(86.51%),但高于初级内镜医师(75.82%)。另外,该模型在精准度、召回率和F1得分方面分别可达84.81%、83.32%和83.95%。模型在多终端设备部署后实现了超过50fps的实时自动Hill分级。结论利用深度学习构建EfficientNet-Hill人工智能模型,实现了针对GEFV形态的自动Hill分级,能够辅助内镜医师提升内镜下分级的诊断效率和准确性,促进Hill分级纳入常规内镜报告和全球胃食管反流病评估中。 展开更多
关键词 胃食管阀瓣 深度学习 卷积神经网络 hill分级 可解释性分析技术 人工智能辅助系统 迁移学习
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Evaluating the Association between Human Papillomavirus and Vulvar Cancer:A Comprehensive Analysis Using Bradford Hill Criteria
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作者 Hamid Yaz 《Journal of Clinical and Nursing Research》 2024年第7期208-218,共11页
Background:The role of human papillomavirus(HPV)in the development of vulvar cancer(VC)has been widely studied,but findings have been inconsistent.Despite numerous meta-analyses exploring the potential link between HP... Background:The role of human papillomavirus(HPV)in the development of vulvar cancer(VC)has been widely studied,but findings have been inconsistent.Despite numerous meta-analyses exploring the potential link between HPV and VC,the association remains controversial due to inherent limitations in meta-analytic methods.Objectives:To address this controversy,the study aims to investigate the potential link between HPV and VC using the Bradford Hill criteria,which offer a more comprehensive framework for establishing causation.Methodology:The study began by extracting all relevant studies on the association between HPV and VC from the PubMed database.The potential links were then assessed by examining the data using the major postulates of the Bradford Hill criteria.To ensure the reliability of the findings,the methodologies of the identified studies were critically evaluated to account for possible false-negative and false-positive results.Results:The assessment of previous studies against the Bradford Hill criteria revealed that the major postulates were not fulfilled.Conclusion:Based on the findings,it can concluded that there is no causal association between HPV and VC. 展开更多
关键词 Vulvar cancer(VC) Bradford hill criteria Human papillomavirus(HPV)
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基于Hill肌肉模型的仿袋鼠腿悬架控制特性研究
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作者 宋勇 刘世静 +2 位作者 李占龙 孟杰 张喜清 《太原科技大学学报》 2023年第5期403-409,共7页
为进一步改善车辆悬架的控制性能,采用仿生设计思想,提出一种基于Hill肌肉模型的仿袋鼠腿悬架(下称仿生悬架)。设计了该悬架的Fuzzy、Fuzzy-PID控制器,并采用ADAMS和Simulink联合仿真对其控制特性开展研究。研究发现:①冲击路面下,相对... 为进一步改善车辆悬架的控制性能,采用仿生设计思想,提出一种基于Hill肌肉模型的仿袋鼠腿悬架(下称仿生悬架)。设计了该悬架的Fuzzy、Fuzzy-PID控制器,并采用ADAMS和Simulink联合仿真对其控制特性开展研究。研究发现:①冲击路面下,相对于被动悬架,Fuzzy控制和Fuzzy-PID控制下的车身位移和车身加速度分别下降了54%、58%和92%、93%,悬架抗冲击性能明显改善。②随机路面下,随着路面等级和车速的增加,Fuzzy控制和Fuzzy-PID控制均可有效改善悬架的控制性能;相对于被动悬架,主动控制下的悬架表现出更加优异的缓冲隔振性能、路面适应性及稳定性;主动控制下的车身加速度传递率(8.8%~1%)呈下降趋势且数值较小,轮胎动位移(0.19~3.92)mm及其传递率(8.1%~10.5%)呈上升趋势,但数值及变化较小。③冲击路面和随机路面下,相较于Fuzzy控制,Fuzzy-PID控制下的悬架特性更优。上述结果表明,基于Hill肌肉模型的仿生悬架具有良好的控制特性,验证了该仿生思路和控制方法的正确性和有效性。 展开更多
关键词 悬架 hill肌肉模型 FUZZY控制 FUZZY-PID控制 仿袋鼠腿
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基于肌球蛋白粗丝力学感知效应的Hill特性式理论研究
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作者 赵晓阳 孙伟 +1 位作者 张俊萍 塔拉 《内蒙古大学学报(自然科学版)》 CAS 北大核心 2023年第6期621-628,共8页
粗丝的机械力学感知效应对于理解肌肉收缩的内在机制具有非常重要的作用。Hill特性式是描述肌肉收缩中负荷与速度关系的经验表达式,对其理论机制的研究中缺乏对粗丝力学感知效应的考虑。本文以肌肉收缩的滑行理论为依据,考虑粗丝的力学... 粗丝的机械力学感知效应对于理解肌肉收缩的内在机制具有非常重要的作用。Hill特性式是描述肌肉收缩中负荷与速度关系的经验表达式,对其理论机制的研究中缺乏对粗丝力学感知效应的考虑。本文以肌肉收缩的滑行理论为依据,考虑粗丝的力学感知效应,建立肌球蛋白与肌动蛋白丝结合的数量与粗丝承受外力的关系模型,从肌肉收缩过程中肌肉内部力的平衡角度出发,推导出肌肉收缩过程中负荷与收缩速度之间的关系即Hill特性式。结果显示理论关系式与Hill特性式完全一致,说明了肌球蛋白的力学感知效应模型的合理性,为揭示肌肉收缩的力与速度关系的潜在机制提供新的视角。 展开更多
关键词 肌肉收缩 力学感知效应 hill特性式
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Decipher hydrocarbon generation and accumulation based on fluid inclusion and chronology:A case study from the Upper Paleozoic buried-hills in Huanghua Depression,Bohai Bay Basin 被引量:1
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作者 Li-Hong Zhou Yong Li +5 位作者 Feng-Ming Jin Jin-Feng Xie Xiu-Gang Pu Li-Xin Fu Da Lou Yang Tian 《Petroleum Science》 SCIE EI CAS CSCD 2023年第4期1998-2008,共11页
Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets.Taking the Upper Paleozoic buried-hills in the Huanghua Depression,Bohai Ba... Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets.Taking the Upper Paleozoic buried-hills in the Huanghua Depression,Bohai Bay Basin,as a case study,hydrocarbon generation environment and detailed accumulation process are revealed by fluid inclusions observations,Laser Raman spectroscopy,Fourier Infrared spectroscopy,and K-Ar isotope measurements.The results show that both oil and gas inclusion were captured in the quartz overgrowth,dissolved feldspar and calcite microfractures,showing blue to dark brown fluoresce.The grains containing oil inclusions index(GOI)of oil,oil&gas and gas being 25%,65%,and 10%and the inclusions with abundant methyl groups and short chains,both indicate high thermal maturity.One series of fluids inclusion is generally observed,evidenced by the concentrated homogenization temperature of 135-145℃ and salinity of 3%-15 w.t.%NaCl equiv,indicating one primary charging stage.The gas and gas&liquid inclusions mainly contain CH_(4),with also peaks indicating CO_(2) and N_(2.)The Carboniferous and Permian biomarkers show reducing environment with brackish water,with organic matter sources both from marine and continental.The relative content ofααα20RC_(27),ααα20RC_(28),andααα20RC_(29) exhibit source contributions both from algae and higher plants,and mainly of II2 to III kerogen.Both coal derived gas and oil associated hydrocarbons are identified from most of the buried-hills.Combining the fluid homogenization temperature and salinity,as well as the thermal evolution history,the hydrocarbon generated from the Upper Paleozoic was concentrated at the end of the Eocene(40 Ma±),while the beginning of charging is 60 Ma±.The Wumaying Buried-hill is of only coal derived gas and has potential for inner coal measure natural gas exploration.The results provide a detailed understanding of hydrocarbon accumulations in the study area,which can also be reference for improving petroleum exploration efficiency in similar basins. 展开更多
关键词 Petroleum accumulation Buried hills K–Ar isotope Fluid inclusions Huanghua depression Bohai Bay Basin
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A Darcy-Law Based Model for Heat and Moisture Transfer in a Hill Cave 被引量:1
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作者 Fei Liu Dongliang Zhang +1 位作者 Qifu Zhu Qingyong Su 《Fluid Dynamics & Materials Processing》 EI 2023年第9期2345-2359,共15页
A hill can be regarded as an environmental carrier of heat.Water,rocks and the internal moisture naturally pre-sent in such environment constitute a natural heat accumulator.In the present study,the heat and moisture ... A hill can be regarded as an environmental carrier of heat.Water,rocks and the internal moisture naturally pre-sent in such environment constitute a natural heat accumulator.In the present study,the heat and moisture trans-fer characteristics in a representative hill cave have been simulated via a method relying on the Darcy’s law.The simulations have been conducted for both steady and unsteady conditions to discern the influence of permeability and geometric parameters on the thermal and moisture transfer processes.The reliability of the simulation has been verified through comparison of the numerical results with the annual observation data.As revealed by the numericalfindings,the internal temperature of the hill accumulator is proportional to the permeability,outside surface temperature,overground height,underground constant temperature layer depth,and underground tem-perature of the hill,and it is inversely proportional to the horizontal size of the hill.Moreover,in the considered case,the order of magnitude of the permeability of the hill is contained in the range 10-15–10-13,and displays a certain sensitivity to the rainwater seepage. 展开更多
关键词 Cave hill thermal and moisture transfer Darcy’s law temperaturefield PERMEABILITY
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Hill Matrix and Radix-64 Bit Algorithm to Preserve Data Confidentiality
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作者 Ali Arshad Muhammad Nadeem +6 位作者 Saman Riaz Syeda Wajiha Zahra Ashit Kumar Dutta Zaid Alzaid Rana Alabdan Badr Almutairi Sultan Almotairi 《Computers, Materials & Continua》 SCIE EI 2023年第5期3065-3089,共25页
There are many cloud data security techniques and algorithms available that can be used to detect attacks on cloud data,but these techniques and algorithms cannot be used to protect data from an attacker.Cloud cryptog... There are many cloud data security techniques and algorithms available that can be used to detect attacks on cloud data,but these techniques and algorithms cannot be used to protect data from an attacker.Cloud cryptography is the best way to transmit data in a secure and reliable format.Various researchers have developed various mechanisms to transfer data securely,which can convert data from readable to unreadable,but these algorithms are not sufficient to provide complete data security.Each algorithm has some data security issues.If some effective data protection techniques are used,the attacker will not be able to decipher the encrypted data,and even if the attacker tries to tamper with the data,the attacker will not have access to the original data.In this paper,various data security techniques are developed,which can be used to protect the data from attackers completely.First,a customized American Standard Code for Information Interchange(ASCII)table is developed.The value of each Index is defined in a customized ASCII table.When an attacker tries to decrypt the data,the attacker always tries to apply the predefined ASCII table on the Ciphertext,which in a way,can be helpful for the attacker to decrypt the data.After that,a radix 64-bit encryption mechanism is used,with the help of which the number of cipher data is doubled from the original data.When the number of cipher values is double the original data,the attacker tries to decrypt each value.Instead of getting the original data,the attacker gets such data that has no relation to the original data.After that,a Hill Matrix algorithm is created,with the help of which a key is generated that is used in the exact plain text for which it is created,and this Key cannot be used in any other plain text.The boundaries of each Hill text work up to that text.The techniques used in this paper are compared with those used in various papers and discussed that how far the current algorithm is better than all other algorithms.Then,the Kasiski test is used to verify the validity of the proposed algorithm and found that,if the proposed algorithm is used for data encryption,so an attacker cannot break the proposed algorithm security using any technique or algorithm. 展开更多
关键词 CRYPTOGRAPHY symmetric cipher text ENCRYPTION matrix cipher encoding decoding hill matrix 64-bit encryption
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Efficient Clustering Using Memetic Adaptive Hill Climbing Algorithm in WSN
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作者 M.Manikandan S.Sakthivel V.Vivekanandhan 《Intelligent Automation & Soft Computing》 SCIE 2023年第3期3169-3185,共17页
Wireless Sensor Networks are composed of autonomous sensing devices which are interconnected to form a closed network.This closed network is intended to share sensitive location-centric information from a source node ... Wireless Sensor Networks are composed of autonomous sensing devices which are interconnected to form a closed network.This closed network is intended to share sensitive location-centric information from a source node to the base station through efficient routing mechanisms.The efficiency of the sensor node is energy bounded,acts as a concentrated area for most researchers to offer a solution for the early draining power of sensors.Network management plays a significant role in wireless sensor networks,which was obsessed with the factors like the reliability of the network,resource management,energy-efficient routing,and scalability of services.The topology of the wireless sensor networks acts dri-ven factor for network efficiency which can be effectively maintained by perform-ing the clustering process effectively.More solutions and clustering algorithms have been offered by various researchers,but the concern of reduced efficiency in the routing process and network management still exists.This research paper offers a hybrid algorithm composed of a memetic algorithm which is an enhanced version of a genetic algorithm integrated with the adaptive hill-climbing algorithm for performing energy-efficient clustering process in the wireless sensor networks.The memetic algorithm employs a local searching methodology to mitigate the premature convergence,while the adaptive hill-climbing algorithm is a local search algorithm that persistently migrates towards the increased elevation to determine the peak of the mountain(i.e.,)best cluster head in the wireless sensor networks.The proposed hybrid algorithm is compared with the state of art clus-tering algorithm to prove that the proposed algorithm outperforms in terms of a network life-time,energy consumption,throughput,etc. 展开更多
关键词 Wireless sensor networks TOPOLOGY CLUSTERING memetic algorithm adaptive hill climbing algorithm network management energy consumption THROUGHPUT
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Reconstruction Design of Zaozhuang Gangue Hill Based on the Interaction of“Scenery”and“View”
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作者 CAO Ying LIANG Zhiwei ZHANG Li 《Journal of Landscape Research》 2023年第4期9-16,共8页
Gangue hill is the associated accumulation landscape of long-term coal mining.There are a large number of gangue hills left in coal mining cities,which not only causes ecological damage but also affects the urban envi... Gangue hill is the associated accumulation landscape of long-term coal mining.There are a large number of gangue hills left in coal mining cities,which not only causes ecological damage but also affects the urban environment,thus becoming the focus of urban landscape transformation of coal mining cities.With the increase of people’s demand for ecological leisure,it has become the first choice to transform gangue hill and its surrounding areas into community parks.From the perspective of urban space and landscape system,as a huge regeneration landform in the city and a unique landscape in the mining area,gangue hill not only needs to be afforested,but also needs to be connected with mining heritages and landscape nodes in the city to form the interaction between“scenery”and“view”,so as to form an integrated mining cultural landscape system at the urban level.On the basis of this concept,taking the gangue hill of Zhongxing in Zaozhuang City as an example,this paper quantitatively analyzes the best landscape construction site in the gangue hill via viewshed analysis in GIS.Through this method,the gangue hill and Zhongxing mining heritage are closely combined,so as to establish the interactive relationship between“scenery”and“view”.It can guide the planning and design of sightseeing route and footpath system,and also provide a technical support for the design of community parks transformed from gangue hills. 展开更多
关键词 Gangue hill Zhongxing mining heritage Interaction of“scenery”and“view” Viewshed analysis
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Petrographic Characteristics and Metalogeny of Zatua Hills BIFs, Haut-Uele Province (DR Congo)
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作者 Levesque Makuku Mbo Papy-Fidèle Kombie Andeibal +3 位作者 François Tshiabo Luwanda Dominique Wetshondo Osomba Valentin Kanda Nkula Albert Ongendangenda Tienge 《Journal of Geoscience and Environment Protection》 2023年第12期163-181,共19页
Zatua Hills are located at Haut Uélé Province of Democratic Republic of Congo (DRC), between northern Bafwasende and southern Paulis (Isiro) Squarred Degrees. Belonging to greenstone belt of Ngayu, that area... Zatua Hills are located at Haut Uélé Province of Democratic Republic of Congo (DRC), between northern Bafwasende and southern Paulis (Isiro) Squarred Degrees. Belonging to greenstone belt of Ngayu, that area is identified by the high elevated zone which is remained the witness of stable zone, not affected by the ancienst erosion process. Zatua Hills are in the superior Kibalian formation dated to Neoarchaen, hosted in Upper Congo Granites Massifs of DRC covering a large central zone of NE of DRC, and consisting to dolerite, phyllade, clay rich sediment, poor Banded Iron Formations (BIFs), enriched BIFs, friable hematite, hard hematite, mineralized and unmineralized brechias. Magnetite, martite and hematite are associated to some secondary minerals such as goethite, gibbsite, kaolinite, strengite, variscite and others clay minerals present in BIFs. Petrographic analysis made from the samples collected in situ showed, as well as BIFs and iron ore associated, that magnetite was much abundant oxide mineral which is oxided to martite before to stabilize to hematite during the deposition time. Having about hundred meters of thickness, the rich iron ore of this area content, in the majority less deleterious elements which, are harmful in metallurgic process of iron. These secondary minerals were precipitated at various degrees in the leached cavities of rocks between martite and hematite aggregates to botryoidal texture and, are rich to Al, and are mainly consisting to gibbsite and solid solution series of variscite-strengite (AlPO<sub>4</sub>·2H<sub>2</sub>O and FePO<sub>4</sub>·2H<sub>2</sub>O). Low degree of metamorphism played when magnetite was converted to martite, with the presence of variscite and anatase like witnesses of this event in which, martite was crystalized to hematite. 展开更多
关键词 BIFs Zatua hills Petrographic DRC Iron Ore
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Geochemical Signature and Metalogeny of BIFs and Associated Iron Ore of Zatua Hills, Haut-Uele Province (DR Congo)
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作者 Levesque Makuku Mbo Dominique Wetshondo Osomba +2 位作者 Valentin Kanda Nkula Kelly Nzambe Keyila Albert Ongendangenda Tshiende 《Journal of Geoscience and Environment Protection》 2023年第10期201-217,共17页
Zatua Hills are located in the northeastern part of the DR Congo in Haut Uélé Province, formerly known as Province Orientale. This part of DR Congo is identified by the high elevated zone, which has rem... Zatua Hills are located in the northeastern part of the DR Congo in Haut Uélé Province, formerly known as Province Orientale. This part of DR Congo is identified by the high elevated zone, which has remained a witness to a stable zone not affected by the ancient erosion process. BIFs are most abundant and are dated to the Neoarchaean and Late Kibalian, hosted in the Upper Congo Granites Massifs of the DR. Congo. Zatua Hills consist of dolerite, phyllade, clay-rich sediment, poor itabirite, enriched BIFs, friable hematite, hard hematite, and mineralized and unmineralized breccias. Field study and geochemistry analysis by XRF, XRD, and ICP-MS are executed in order to know the geochemistry signature and paragenesis of Zatua Hills and the probably process could lead the BIFs to iron ore. The geochemistry analysis by XRF, XRD, and ICP-MS shows that Iron ore content has an iron rate between 57% and 69% with less deleterious elements such as Si, P, and Al. These deleterious elements are secondary and have silicium composition (probably quartz or chert, goethite, and Kaolinite), aluminum (probably gibbsite, variscite, cadwaladérite, goethite, and Kaolinite), phosphorous (probably variscite), and hydrated minerals, which are grown LOI in the samples. Hypogen and supergen processes are played in BIFs for iron ore conversion and, respectively, silica dissolution and leaching. Metamorphism was also impacted and marked by the Ti element (anatase) in samples, contributing to the crystallization of martite to hematite after magnetite oxidation. 展开更多
关键词 BIFs Zatua hills Geochemestry DRC Iron Ore
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The Awakening of Consciousness:Traumatic Repetition in“Funeral Music”by Geoffrey Hill
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作者 XING Luan-ming 《Journal of Literature and Art Studies》 2023年第9期661-664,共4页
The aftermath of the war had devastating consequences on people’s lives and society as a whole.In addition to the significant impact of the Great Depression on social production and living standards,it resulted in ps... The aftermath of the war had devastating consequences on people’s lives and society as a whole.In addition to the significant impact of the Great Depression on social production and living standards,it resulted in psychological trauma,unemployment,poverty,and social conflicts.As a prominent English poet that emerged after World War II,Geoffrey Hill depicted the gruesome realities of war through his early works.This article applies Cathy Caruth’s trauma theory to analyze Hill’s poem“Funeral Music.”The fragmented images and repetitive traumatic scenes restore the harsh realities of war.Furthermore,this article explores Joshua Pederson’s critical development of Caruth’s theoretical framework,providing an alternate perspective for textual analysis. 展开更多
关键词 TRAUMA Geoffrey hill “Funeral Music” Cathy Caruth Joshua Pederson
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Experimental Study on Phase Characteristics of CO2 Injection in BZ13-2 Strong Volatile Oil Reservoir in Bohai Sea Buried Hills
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作者 Zhennan Gao Lei Zhang +2 位作者 Yong Jiang Jingtao Wu Chenxu Yang 《Open Journal of Geology》 2023年第7期763-772,共10页
BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure.... BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO<sub>2</sub> injection to improve oil recovery in near critical volatile oil reservoirs through CO<sub>2</sub> injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO<sub>2</sub> injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO<sub>2</sub> injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery. 展开更多
关键词 Bohai Buried hills Strongly Volatile Reservoir Gas Injection and Development Phase Characteristics Fine Tube Experiment
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Identification and evaluation of fault-fracture reservoirs in buried hills of the Lower Paleozoic, Chengdao area, China
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作者 Zhiwei Wang Kai Zhang +1 位作者 Yuhan Cheng Qunhu Wu 《Energy Geoscience》 2023年第3期193-202,共10页
The Bohai Bay Basin is a Meso-Cenozoic rifted basin where the Paleozoic buried hills with great hydrocarbon potentials are well developed. The reservoir space types are complex and diverse due to tectonic activities, ... The Bohai Bay Basin is a Meso-Cenozoic rifted basin where the Paleozoic buried hills with great hydrocarbon potentials are well developed. The reservoir space types are complex and diverse due to tectonic activities, making fracture distribution highly heterogeneous. Reservoir identification and mapping is challenging due to their large burial depth and poor resolution of seismic data. An integration of well-logging, seismic data interpretation and core observation is applied to identify three structural unit types in the study area, that is, fault breccia zone, fault cataclastic zone, and fault massive rock zone. A comprehensive well-logging identification template and a comprehensive discriminant function M for the reservoir are established based on the well-logging response characteristics. A M value greater than 0.12 indicates a fault breccia zone, that between 0.04 and 0.12 marks a fault cataclastic zone, and that in the range from 0.02 to 0.04 represents a fault massive rock zone. A seismic prediction method with multi-parameter fusion is proposed in the study. The large-scale fractures are mapped by coherence-clutter parameters, while small fractures are predicted via waveform indication inversion. The spatial distribution of “fault-fracture reservoirs” is precisely mapped by frequency fusion technology. It is found that the fault breccia zones usually occur close to the fault planes, while the fault cataclastic zones are slightly away from the fault planes. The hydrocarbon abundance of the breccia zones is greater than that of the fault cataclastic and fault massive rock zones. 展开更多
关键词 Buried hill Fault-facture Ieservoir Reservoir logging identication Reservoir sei smnic mapping Lower paleozoic Chengdao area
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Distributed Trimmed Hill Estimator
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作者 Tao Guo 《Journal of Applied Mathematics and Physics》 2023年第12期4000-4015,共16页
Proceeded from trimmed Hill estimators and distributed inference, a new distributed version of trimmed Hill estimator for heavy tail index is proposed. Considering the case where the number of observations involved in... Proceeded from trimmed Hill estimators and distributed inference, a new distributed version of trimmed Hill estimator for heavy tail index is proposed. Considering the case where the number of observations involved in each machine can be either the same or different and either fixed or varying to the total sample size, its consistency and asymptotic normality are discussed. Simulation studies are particularized to show the new estimator performs almost in line with the trimmed Hill estimator. 展开更多
关键词 Extreme Value Index Distributed Trimmed hill Estimator
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截面型式及槽宽比对高填明洞土压力影响分析
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作者 何永泽 李盛 +3 位作者 后浩斌 马莉 贡力 余云燕 《应用力学学报》 CAS CSCD 北大核心 2024年第2期330-339,共10页
利用离散元软件PFC2D,考虑到土体的离散性与不均匀性,通过分析洞顶平均竖向土压力、内外土柱相对沉降差以及颗粒间接触力链的变化规律,探讨截面型式(矩形、1/4拱形、1/2拱形)及槽宽比(B/b=1.5∶1,2∶1,3∶1,4∶1)变化对高填黄土明洞土... 利用离散元软件PFC2D,考虑到土体的离散性与不均匀性,通过分析洞顶平均竖向土压力、内外土柱相对沉降差以及颗粒间接触力链的变化规律,探讨截面型式(矩形、1/4拱形、1/2拱形)及槽宽比(B/b=1.5∶1,2∶1,3∶1,4∶1)变化对高填黄土明洞土压力的影响,结合顾安全公式,分析高填明洞沉降差与土压力间的函数关系,并修正该函数,使其可以适用与不同的截面型式与槽宽比下的高填明洞。结果表明:(1)B/b确定,明洞采用矩形截面时,接触力链在洞顶分布,平均土压力更大,明洞采用拱形截面时,平均土压力更小,但拱顶存在局部应力集中现象;(2)明洞截面型式一定,随着B/b的增大,洞顶平均竖向土压力与沉降差均随之增大,当B/b较小时,边坡作用增强,外侧土柱沉降降低,对内土柱的作用力变小,从而导致明洞顶竖向土压力更小;(3)内外土柱沉降差与附加土压力呈线性相关,相对于矩形截面,拱形截面下较小的沉降差会产生相同的附加土压力,更有利于结构的稳定。 展开更多
关键词 高填明洞 截面型式 槽宽比(B/b) PFC2D 土压力 沉降差
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极值理论中阈值选取的Hill估计方法改进 被引量:15
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作者 宋加山 李勇 +2 位作者 彭诚 王彪 方兆本 《中国科学技术大学学报》 CAS CSCD 北大核心 2008年第9期1104-1108,共5页
利用变点统计理论对极值理论中阈值选择的传统Hill估计方法进行了改进,实现了阈值的定量精确选取,从而减少了因主观判断所引起的阈值选取偏差.将此方法应用到基于极值理论的商业银行操作风险度量中,取得了较好的效果.
关键词 hill估计 变点 阈值
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镉胁迫对续断菊Sonchus asper L.Hill.根系分泌物的影响 被引量:14
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作者 秦丽 李元 +3 位作者 祖艳群 何永美 王吉秀 陈建军 《生态环境学报》 CSCD 北大核心 2012年第3期540-544,共5页
通过盆栽试验,研究了不同Cd质量分数(0、50、100、200 mg.kg-1)对续断菊Sonchus asper L.Hill.根系分泌总有机酸、游离氨基酸、可溶性糖的影响,旨在探明根系分泌物对续断菊超积累Cd的影响。结果表明:Cd胁迫下续断菊根系分泌总有机酸、... 通过盆栽试验,研究了不同Cd质量分数(0、50、100、200 mg.kg-1)对续断菊Sonchus asper L.Hill.根系分泌总有机酸、游离氨基酸、可溶性糖的影响,旨在探明根系分泌物对续断菊超积累Cd的影响。结果表明:Cd胁迫下续断菊根系分泌总有机酸、游离氨基酸和可溶性糖的质量浓度显著增加,同时,总有机酸、可溶性糖和游离氨基酸又促进了植株对Cd的吸收。随着Cd处理质量分数的增加,续断菊地上部和根部镉质量分数显著增加,90 d时续断菊地上部镉质量分数与可溶性糖、游离氨基酸的质量浓度呈极显著正相关,相关系数分别为0.999(P<0.01)和0.995(P<0.01),根部镉质量分数与可溶性糖、游离氨基酸的质量浓度也呈显著正相关,相关系数分别为0.998(P<0.01)和0.987(P<0.05);Cd对续断菊根系可溶性糖的分泌、游离氨基酸的合成有刺激作用,根系分泌的可溶性糖和游离氨基酸可能在续断菊累积镉的过程中有重要作用。 展开更多
关键词 CD 续断菊Sonchus asper L.hill. 根系分泌物 可溶性糖 游离氨基酸
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Habitat Utilization of the Sichuan Hill Partridge (Arborophila rufipectus) in the Non-breeding Period in Laojunshan Nature Reserve 被引量:10
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作者 廖文波 李操 +1 位作者 胡锦矗 卢欣 《Zoological Research》 CAS CSCD 北大核心 2007年第2期172-178,共7页
The Sichuan Hill Partridge (Arborophila rufipectus ) requires successional broadleaf forest and their populations have declined as a result of fragmentation of endemic bird areas in subtropical forest in the mountai... The Sichuan Hill Partridge (Arborophila rufipectus ) requires successional broadleaf forest and their populations have declined as a result of fragmentation of endemic bird areas in subtropical forest in the mountains of southwestern China. In this paper, habitat utilization of the Sichuan Hill Partridge was studied in replanted broadleaf forests, in Laojunshan Nature Reserve of Sichuan, to determine the importance of habitat features, during the non-breeding period from November to December 2005. The Sichuan Hill Partridge utilized habitats within elevations of 1 000 to 1 600 m and with a south-facing slope of two to 15 degrees, close to road and forest edges. The birds preferred sites with smaller bamboo density, lower bamboo cover and snow cover and shrub cover was greater at used sites than at random sites. Principal components analysis indicated that food on the ground layer, topographic condition, concealment and temperature were the first four components of bird habitat selection, and the load of the first component was 29.407%. The findings indicated that the Sichuan Hill Partridge might face the well-documented trade-off between food resource and predation risk when utilizing habitat. We suggest that the conservation and restoration of successional broadleaf forest habitats will benefit the Sichuan Hill Partridge. 展开更多
关键词 Sichuan hill Partridge (Arborophila rufipectus Ecological factors Non-breeding period Habitat utilization
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