期刊文献+
共找到223篇文章
< 1 2 12 >
每页显示 20 50 100
Investigation on mechanical properties regulation of rock-like specimens based on 3D printing and similarity quantification
1
作者 Duanyang Zhuang Zexu Ning +3 位作者 Yunmin Chen Jinlong Li Qingdong Li Wenjie Xu 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2024年第5期573-585,共13页
3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properti... 3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properties of 3D-printed specimens to make them proportionally similar to natural rocks.This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles.The mechanical property regulation of 3D-printed specimens is realized through quantifying its similarity to sandstone,so that analogous deformation characteristics and failure mode are acquired.Considering similarity conversion,uniaxial compressive strength,cohesion and stress–strain relationship curve of 3D-printed specimen are similar to those of sandstone.In the study ranges,the strength of 3D-printed specimen is positively correlated with the additive content,negatively correlated with the sand particle size,and first increases then decreases with the increase of curing temperature.The regulation scheme with optimal similarity quantification index,that is the sand type of 70/140,additive content of 2.5‰and curing temperature of 81.6℃,is determined for preparing 3D-printed sandstone analogues and models.The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests.This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology. 展开更多
关键词 3D printing Mechanical property regulation similarity quantification Rock analogue SANDSTONE
下载PDF
Mechanical Property Estimation of Similar Weld using Ball Indentation Technique 被引量:1
2
作者 Harshit Kumar Khandelwal Kamal Sharma Rahul Chhibber 《Journal of Minerals and Materials Characterization and Engineering》 2012年第11期1095-1110,共16页
A weld joint is composed of three principal zones viz., base metal, Heat Affected Zone (HAZ), and weld zone. Thus, the variation in mechanical behavior exists not only among these zones, but also from point to point i... A weld joint is composed of three principal zones viz., base metal, Heat Affected Zone (HAZ), and weld zone. Thus, the variation in mechanical behavior exists not only among these zones, but also from point to point in each individual zone. Being destructive in nature, the conventional method of mechanical testing cannot successfully used to estimate the variation in the mechanical behavior at different zones of the weld joint. Moreover, the conventional method of mechanical testing cannot characterize the material using small amount of material. In this respect, Ball Indentation (BI) methodology was considered to be useful approach, since it can characterize the mechanical properties of a material using very small amount of material in non destructive manner. The present work is an attempt to characterize the variation in the mechanical properties among each zone (global variation), and from point to point in each zone (local variation) of the similar weld joint used in nuclear application using BI approach. For this purpose, the similar weld joint of two SS-304 LN pipe lines was investigated using BI approach. 展开更多
关键词 BALL INDENTATION In SITU similar WELD Joint Flow Properties Pressurized Water REACTOR REACTOR Pressure VESSEL
下载PDF
基于地理最优相似性的土壤重金属镉含量空间预测
3
作者 廖秀英 王波 +3 位作者 余昕 梁继 程辉 田茂军 《中南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第6期2143-2152,共10页
以地理相似性定律为基础,利用野外采集的40个土壤样本数据,结合环境辅助变量构建地理最优相似性(GOS)模型,对研究区域重金属镉含量及其空间分布进行预测研究,并将预测结果与偏最小二乘回归(PLSR)、随机森林(RF)和通用克里格(UK)模型的... 以地理相似性定律为基础,利用野外采集的40个土壤样本数据,结合环境辅助变量构建地理最优相似性(GOS)模型,对研究区域重金属镉含量及其空间分布进行预测研究,并将预测结果与偏最小二乘回归(PLSR)、随机森林(RF)和通用克里格(UK)模型的结果进行对比分析。研究结果表明:研究区内土壤样本镉质量分数均值(0.432 mg/kg)比背景值大,接近中度污染水平(污染指数为2.18),区域土壤生态环境受到一定的威胁;GOS预测结果的决定系数为0.668,均方根误差和平均绝对误差分别为0.096和0.080,在4个预测模型中表现最佳;区域重金属Cd质量分数从东北部向西南部递减,高值分布于河流沿岸和人类活动密集区域,反映出人类活动是导致研究区内土壤重金属分异的主要因素。 展开更多
关键词 地理相似性 土壤属性 重金属CD 空间预测
下载PDF
复杂散体状顶板回采巷道围岩注浆改性控制分析 被引量:1
4
作者 张继远 任金武 +3 位作者 辛亚军 张盼 张增光 吴春浩 《金属矿山》 CAS 北大核心 2024年第4期228-235,共8页
复杂散体状顶板巷道围岩破坏严重,变形量大,支护困难。通过对复杂散体状顶板巷道围岩变形破坏特征与失稳原因分析,研究了不同配比似膏体注浆材料的浆液密度、析水率、流动度特征,探明了不同水灰比、粉煤灰掺量对似膏体注浆材料强度的影... 复杂散体状顶板巷道围岩破坏严重,变形量大,支护困难。通过对复杂散体状顶板巷道围岩变形破坏特征与失稳原因分析,研究了不同配比似膏体注浆材料的浆液密度、析水率、流动度特征,探明了不同水灰比、粉煤灰掺量对似膏体注浆材料强度的影响机制,确定了似膏体注浆材料优化配比与注浆加固支护方案。结果表明:复杂散体状顶板巷道围岩表现为顶板破坏严重呈网兜状下沉,高低帮呈整体“凹”型膨胀变形;散块体、弱胶结、高应力、软煤体、支护失效是巷道围岩失稳的主要原因;随着水灰比、粉煤灰掺量增大,浆液析水率与流动度呈增加趋势、浆液密度则呈降低趋势,水灰比对浆液流动度影响大于粉煤灰掺量;浆液结石体破坏强度随着水灰比与粉煤灰掺量的提高分别表现为加速衰减姿态与急剧下降—缓慢增加—缓慢下降趋势;似膏体注浆材料优化配比的水灰比与粉煤灰掺量分别为0.6∶1与80%;采用锚杆(索)+似膏体注浆控制技术方案30 d后,顶板最大下沉量小于80 mm,两帮最大收敛量小于70 mm,巷道围岩稳定性较好。 展开更多
关键词 复杂散体 回采巷道 粉煤灰 似膏体浆液 力学特性 稳定性
下载PDF
关帝山不同海拔天然次生杨桦林地表昆虫群落结构及多样性特征分析 被引量:1
5
作者 李蓉姣 董江海 +2 位作者 刘磊 范世明 高瑞贺 《西北林学院学报》 CSCD 北大核心 2024年第4期61-70,共10页
地表昆虫作为森林群落生态系统的重要组成部分,能够加快凋落物分解及土壤生态学过程。为了解关帝山林区地表昆虫群落组成及多样性特征,探讨影响其空间格局分布的环境因子,在关帝山林区典型的天然次生阔叶林生态系统——杨-桦混交林中,... 地表昆虫作为森林群落生态系统的重要组成部分,能够加快凋落物分解及土壤生态学过程。为了解关帝山林区地表昆虫群落组成及多样性特征,探讨影响其空间格局分布的环境因子,在关帝山林区典型的天然次生阔叶林生态系统——杨-桦混交林中,从海拔1 600~2 200 m梯度范围设置4个生境,于2022年的7-8月采用巴氏罐诱法对林下地表昆虫进行2次系统的调查,对不同海拔地表昆虫多样性指数进行单因素方差分析,并利用冗余分析来确定环境因子对地表昆虫多样性的影响。结果表明,1)采集2 449头地表昆虫,隶属于7目30科64种,其中,步甲科和蚁科为优势物种。2)不同海拔地表昆虫群落组成差异明显,其个体数和物种数均随海拔高度的升高呈下降的趋势,不同海拔梯度间地表昆虫群落的相似性系数显示相邻2个海拔之间物种的相似性较高。3)低海拔段的Shannon多样性指数、Pielou均匀度指数和Margalef丰富度指较高,各海拔Pielou均匀度指数无显著差异。4)Pearson相关系数分析表明,土壤的温度、水分及孔隙度是影响地表昆虫物种多样性的主要环境因子;冗余分析也进一步确定温度是影响地表昆虫群落分布最主要的因素。研究结果为关帝山生态系统研究进行重要补充,也为关帝山林区地表昆虫多样性保护提供一定的理论基础。 展开更多
关键词 地表昆虫 海拔梯度 土壤性质 多样性 相似性
下载PDF
基于降低数据稀疏度的协同过滤算法
6
作者 徐文涛 王诚 《计算机技术与发展》 2024年第5期170-174,共5页
协同过滤算法是推荐系统的一种常见算法,其核心思想是通过历史数据挖掘用户偏好,计算对象相似近邻项进行推荐。但是一般真实数据都存在严重的数据稀疏性问题,用户或者项目之间的共同评分项目过少,使得一些传统相似度算法计算不准确、推... 协同过滤算法是推荐系统的一种常见算法,其核心思想是通过历史数据挖掘用户偏好,计算对象相似近邻项进行推荐。但是一般真实数据都存在严重的数据稀疏性问题,用户或者项目之间的共同评分项目过少,使得一些传统相似度算法计算不准确、推荐准确度不高。传统Slope One算法准确度不高,但其实现简单,运行效率高,可以用做稀疏数据预填充,从而改善相似度计算的准确度。因此,结合Slope One算法,该文提出了一种基于降低数据稀疏度的协同过滤算法。首先对用户评分数据进行分层聚类,再使用Weighted Slope One算法对高稀疏度数据集部分空白数据进行预测填充,从而大幅度降低数据稀疏度,提高了皮尔逊相似度计算的准确度,最后再引入对象属性偏好相似度进行融合。通过MovieLens 100 K数据集进行算法验证,从结果中可以清晰地看出其平均绝对误差(Mean Absolute Error,MAE)有所降低,证明该算法能在一定程度上提升推荐结果的准确度。 展开更多
关键词 协同过滤 数据稀疏度 加权Slope One 皮尔逊相似度 对象属性
下载PDF
Method of fabricating artificial rock specimens based on extrusion free forming(EFF)3D printing
7
作者 Xiaomeng Shi Tingbang Deng +2 位作者 Sen Lin Chunjiang Zou Baoguo Liu 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第4期1455-1466,共12页
Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natura... Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation. 展开更多
关键词 Artificial rock 3D printing Extrusion free forming(EFF) similarity analysis Mechanical properties
下载PDF
Refill friction stir spot welding (RFSSW): a review of processing, similar/dissimilar materials joining, mechanical properties and fracture mechanism
8
作者 Yun-qiang Zhao Hao-kun Yang +2 位作者 Aloshyn Andriia Hong-hang Lo Jia-xin Li 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2024年第8期1825-1839,共15页
Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/... Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed. 展开更多
关键词 Refill friction stir spot welding PROCESSING MECHANISM similar materials joining Dissimilar materials joining MICROSTRUCTURE Mechanical property Fracture mechanism
原文传递
Damage and failure characteristics of rock similar materials with pre-existing cracks 被引量:5
9
作者 Xiaoyu Cheng 《International Journal of Coal Science & Technology》 EI 2019年第4期505-517,共13页
In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution ... In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load.The equipment used in this study is the self-developed YYW-Ⅱ strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system.Results show that,as the length of pre-existing crack increases:(1) the peak and residual strength reduces,and the peak axial strain and the strain during the initial compression phase increases;(2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack;(3) The damage increases during the stable and accelerated development stage,and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage. 展开更多
关键词 Pre-existing cracks ROCK similar materials Mechanical properties ACOUSTIC EMISSION LOCALIZATION DAMAGE EVOLUTION
下载PDF
Self-Similar Solutions for a Class of Reaction-Diffusion Systems
10
作者 郭佩芳 《Journal of Southeast University(English Edition)》 EI CAS 1997年第2期116-120,共5页
The self similar solutions for a class of reaction diffusion systems are analyzed. The existence and qualitative properties are discussed.
关键词 REACTION DIFFUSION SYSTEMS self similar SOLUTIONS qualitative properties
下载PDF
Coarse Graining Method Based on Noded Similarity in Complex Network
11
作者 Yingying Wang Zhen Jia Lang Zeng 《Communications and Network》 2018年第3期51-64,共14页
Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex... Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex networks, which is based on the node similarity index. From the information structure of the network node similarity, the coarse-grained network is extracted by defining the local similarity and the global similarity index of nodes. A large number of simulation experiments show that the proposed method can effectively reduce the size of the network, while maintaining some statistical properties of the original network to some extent. Moreover, the proposed method has low computational complexity and allows people to freely choose the size of the reduced networks. 展开更多
关键词 COMPLEX Network Coarse GRAINING NODE similarITY STATISTICAL PROPERTIES
下载PDF
Property combination patterns of traditional Chinese medicines
12
作者 Yanan Hu Jing Sun +1 位作者 Yun Wang Yanjiang Qiao 《Journal of Traditional Chinese Medical Sciences》 2016年第2期110-115,共6页
Objective:In this study,the property combinations(PCs)of single herbs,two-herb combinations,and multi-herb prescriptions were studied to determine that the propertycombination patterns will be associated with these th... Objective:In this study,the property combinations(PCs)of single herbs,two-herb combinations,and multi-herb prescriptions were studied to determine that the propertycombination patterns will be associated with these three levels.Method:By calculating the prescription PC weight,we analyzed the PCs of the single herb coptis rhizome,the two-herb combination of coptis rhizome and scutellaria root,and the classic prescriptions Coptis Decoction to Resolve Toxicity,White Tiger Decoction to Resolve Toxicity,and Peony Decoction,all three of which contain coptis and scutellaria.Results:Calculated results show that cold-bitter-lung,cold-bitter-heart,and cold-bitterstomach are present in both Coptis Decoction and White Tiger Decoction and have the highest PC weights.The weights of coptis and scutellaria in Peony Decoction differs from in their weights in Coptis Decoction and White Tiger Decoction,in that the PCs of highest weights in Peony Decoction are cold-bitter-spleen,cold-bitter-liver,cold-bitter-large intestine,coldsour-liver,and cold-sour-spleen.Conclusion:This novel method for exploring the properties and compatibilities of traditional Chinese herbs helps validate the combination theories of herbs.Application of this method may be valuable in designing new efficacious herbal prescriptions. 展开更多
关键词 property combination property-combination pattern similarITY
下载PDF
On the Preconditioning Properties of RHSS Preconditioner for Saddle-Point Linear Systems
13
作者 Ju-Li Zhang 《Communications on Applied Mathematics and Computation》 2021年第1期177-187,共11页
In this paper,for the regularized Hermitian and skew-Hermitian splitting(RHSS)preconditioner introduced by Bai and Benzi(BIT Numer Math 57:287–311,2017)for the solution of saddle-point linear systems,we analyze the s... In this paper,for the regularized Hermitian and skew-Hermitian splitting(RHSS)preconditioner introduced by Bai and Benzi(BIT Numer Math 57:287–311,2017)for the solution of saddle-point linear systems,we analyze the spectral properties of the preconditioned matrix when the regularization matrix is a special Hermitian positive semidefinite matrix which depends on certain parameters.We accurately describe the numbers of eigenvalues clustered at(0,0)and(2,0),if the iteration parameter is close to 0.An estimate about the condition number of the corresponding eigenvector matrix,which partly determines the convergence rate of the RHSS-preconditioned Krylov subspace method,is also studied in this work. 展开更多
关键词 Saddle-point linear systems RHSS preconditioner Preconditioning properties Matrix similar transformation Condition number of eigenvector matrix
下载PDF
Influence of Soil-Foundation Interaction Properties on Oscillations of the System “Building-Building” and “Building-Stack-Like Structure”
14
作者 Gaibnazar Khodievich Khojmetov Alinazar Irismetovich Khodjimetov Anvar Sayfullaevich Yuvmitov 《World Journal of Mechanics》 2015年第6期106-116,共11页
Seismic oscillations of the “building-building” system which is interconnected buildings built close to each other, and “building-stack-like structure” system which is adjacent and connected in different ways to e... Seismic oscillations of the “building-building” system which is interconnected buildings built close to each other, and “building-stack-like structure” system which is adjacent and connected in different ways to existing building are considered in the paper. Different types of connections, such as dampers, including the ones suggested by the authors, are studied. Seismic impact is given as a harmonic function and various existing accelerograms, including synthesized ones. Distinctive feature of this paper from previously published ones [1] [2] is the fact that the emphasis falls on the influence of soil-foundation interaction properties, which are described using various models of load-displacement connections. Calculation results are compared in the case of representation of the building as concentrated masses and spatial systems. Ways to reduce seismic response of buildings during the earthquakes are pointed out. Results of experimental studies are given in the paper and are compared with calculations. 展开更多
关键词 Interaction PROPERTIES of Soil-Foundation The Rigid FOUNDATION Kelvin-Voigt and Maxwell Models DAMPER the Coulomb’s Force Modeling similarity MULTIPLIERS Dynamic Characteristics OSCILLATIONS Sensors Accelerogram Absorption Factor
下载PDF
An Expected Patch Log Likelihood Denoising Method Based on Internal and External Image Similarity
15
作者 Peng Xu Jianwei Zhang 《Journal on Internet of Things》 2020年第1期13-21,共9页
Nonlocal property is an important feature of natural images,which means that the patch matrix formed by similar image patches is low-rank.Meanwhile,learning good image priors is of great importance for image denoising... Nonlocal property is an important feature of natural images,which means that the patch matrix formed by similar image patches is low-rank.Meanwhile,learning good image priors is of great importance for image denoising.In this paper,we combine the image self-similarity with EPLL(Expected patch log likelihood)method,and propose an EPLL denoising model based on internal and external image similarity to improve the preservation of image details.The experiment results show that the validity of our method is proved from two aspects of visual and numerical results. 展开更多
关键词 Nonlocal property patch matrix internal similarity external similarity
下载PDF
Multi-criteria assessment of offshore wind turbine support structures based on dynamic property optimization
16
作者 孟珣 Shi Ruifeng 《High Technology Letters》 EI CAS 2014年第4期421-428,共8页
Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optim... Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optimization methodology for decision making process of bottom mounted supports of offshore wind turbines (OWTs) through reasonable engineering attributes derivation.Mathematic models of support structures are reduced by the generalized single-degree-of-freedom theory with relatively fewer structural parameters.Soft-stiff design optimization based on dynamic properties of OWTs is performed for monopile and lattice supports with different wind turbines,water depth and hub height.Attributes of support structures,wind turbines and environment conditions are applied in the multi-criteria decision making method——TOPSIS for benchmarking of those options.The results illustrate the effectiveness of the proposed optimazation methodology combined with economical and environmental attributes together. 展开更多
关键词 offshore wind turbines (OWTs) support structure finite element method generalized single-degree-of-freedom (GSDOF) system dynamic property technique for order preference by similarity to ideal solution (TOPSIS) method
下载PDF
不同加载速率下软硬互层类岩石力学及声发射特性 被引量:3
17
作者 康玉梅 谷今 魏梦琦 《东北大学学报(自然科学版)》 EI CAS CSCD 北大核心 2023年第3期399-407,共9页
基于三峡库区砂泥岩互层岩体实测数据,制作软硬互层类岩石试样,在单轴压缩条件下,探究不同静态加载速率对不同厚度比、不同岩层组合方式岩样的力学及声发射特性的影响.研究结果表明:加载速率和硬软岩体积比是影响峰值强度的主要因素,而... 基于三峡库区砂泥岩互层岩体实测数据,制作软硬互层类岩石试样,在单轴压缩条件下,探究不同静态加载速率对不同厚度比、不同岩层组合方式岩样的力学及声发射特性的影响.研究结果表明:加载速率和硬软岩体积比是影响峰值强度的主要因素,而加载速率和硬软岩岩层厚度比是影响最终破坏特征的主要因素.一方面,随着加载速率的增大,软硬互层类岩石峰值强度先减小后增大;硬岩占比与岩样抗压强度呈正相关;另一方面,低加载速率下岩样最终破坏模式为材料充分破坏,较高加载速率下岩样最终形成1~2条贯穿软硬岩层的主破裂面;软岩体积占比越少,软岩受到的破坏程度越剧烈;此外,可以把AF值突增、b值骤降作为软硬互层岩体大面积破坏的预警信号. 展开更多
关键词 软硬互层类岩石 声发射特征 力学特性 破坏特征 相似材料
下载PDF
弱胶结砂岩钻井法凿井破岩类材料试验研究 被引量:1
18
作者 程桦 胡方宇 +2 位作者 郭龙辉 荣传新 王晓云 《安徽理工大学学报(自然科学版)》 CAS 2023年第6期18-28,共11页
为了满足侏罗系弱胶结砂岩钻井法凿井破岩相似模型试验类材料的配制需求,基于其物理力学特性及破岩工况,以抗压强度、抗剪强度、抗拉强度、软化系数和干密度等为主要参数,提出类材料相似条件,选择配制原材料,根据试样正交试验结果,分析... 为了满足侏罗系弱胶结砂岩钻井法凿井破岩相似模型试验类材料的配制需求,基于其物理力学特性及破岩工况,以抗压强度、抗剪强度、抗拉强度、软化系数和干密度等为主要参数,提出类材料相似条件,选择配制原材料,根据试样正交试验结果,分析不同配比类材料的物理力学特性及其影响因素,获得满足破岩相似材料模型要求的类材料最优配比。研究结果表明,水泥石膏比是影响弱胶结砂岩相似材料强度和软化系数的主要影响因素,且两者均与水泥石膏比呈正相关,饱水后的类材料具有显著的软化特征;胶砂比在1∶1至2∶1范围内,类材料水化产物氢氧化钙与二水硫酸钙含量显著增加,富集处易造成裂隙发育,从而降低材料强度;基于正交试验结果,优选的胶砂比为2∶1,水泥石膏比为6∶4,即m砂∶m水泥∶m石膏∶m水∶m减水剂=1∶1.2∶0.8∶0.6∶0.02,其物理力学特性基本满足类材料相似条件要求,可作为弱胶结砂岩破岩相似模型试验的类材料。研究结果可为侏罗系弱胶结地层钻井法破岩提供前期条件和类材料配比提供参考。 展开更多
关键词 弱胶结砂岩 类材料 正交试验 物理力学特性 影响因素
下载PDF
干燥方式对熊胆粉物理特性、紫外及抑菌作用的影响 被引量:3
19
作者 杨俊莉 杨放 +4 位作者 谭瑶琳 钟林江 邓妍 谢晓 徐玉玲 《中国抗生素杂志》 CAS CSCD 北大核心 2023年第2期186-193,共8页
目的考察干燥方式对熊胆粉物理特性、紫外及抑菌作用的影响。方法采用常压、减压及冷冻干燥对熊胆汁进行干燥,对熊胆粉各项物理质量属性指标进行综合表征,建立由8个指标:颗粒间空隙率(Ie)、卡尔指数(IC)、松密度(Da)、振实密度(Dc)、干... 目的考察干燥方式对熊胆粉物理特性、紫外及抑菌作用的影响。方法采用常压、减压及冷冻干燥对熊胆汁进行干燥,对熊胆粉各项物理质量属性指标进行综合表征,建立由8个指标:颗粒间空隙率(Ie)、卡尔指数(IC)、松密度(Da)、振实密度(Dc)、干燥失重(%HR)、吸湿性(%H)、豪纳斯比(IH)、休止角(α)构成的物理指纹图谱,以雷达图定量直观展示并比较其物理特性差异。以相似度分析,聚类分析(CA),主成分分析(PCA)等多元统计分析方法对不同干燥方式生产的9批熊胆粉进行质量评价,找出样品批间差异性指标。采用紫外可见分光光度计分别扫描9批熊胆粉溶液全波长图谱,建立对照紫外可见图谱,用相关系数法计算样品指纹图谱与对照指纹图谱的相似度。采用牛津杯抑菌法测定3种干燥方式(常压干燥、减压干燥、冷冻干燥)熊胆粉对大肠埃希菌、金黄色葡萄球菌及枯草芽胞杆菌的体外抑菌值;结果相同干燥方式所得熊胆粉物理及紫外指纹谱间相似度较大,不同干燥方式所得熊胆粉物理指纹图谱间相似度为57.1%~92.9%,其紫外指纹图谱间相似度不低于91.3%。干燥方式导致物理属性指标有一定差异,其主要差异性指标分别为颗粒间空隙率、干燥失重、卡尔指数、休止角、吸湿性。3种干燥方式熊胆粉均对大肠埃希菌、金黄色葡萄球菌、枯草芽胞杆菌有抑菌作用,其中冷冻干燥熊胆粉抑菌作用最弱,与常压干燥、减压干燥组比较,有显著性差异(P<0.05,P<0.01);结论干燥方式对熊胆粉物理特性有一定影响,对其紫外指纹图谱无较大影响,但对熊胆粉抑菌作用有较大影响。该方法从物理状态层面评价熊胆粉批间的质量一致性,可反映生产工艺对熊胆粉物理性质的影响,为后续制剂的质量控制研究提供新思路。 展开更多
关键词 熊胆粉 减压干燥 物理特性 紫外指纹图谱 抑菌作用 相似度
下载PDF
不同放牧强度对高寒草甸土壤种子库的影响 被引量:1
20
作者 许明圆 朱文琰 +4 位作者 杨畅 王娅琳 徐世晓 赵凌平 孙平 《草业科学》 CAS CSCD 北大核心 2023年第6期1461-1471,共11页
以青海省贵南县高寒草甸为研究对象,采用地上植被调查和室内萌发试验相结合的方法,对不同放牧强度下土壤种子库的特征及其与地上植被的关系进行研究,并探讨放牧条件下地上植被、土壤种子库和土壤理化性质三者的联系,拟为高寒地区的植被... 以青海省贵南县高寒草甸为研究对象,采用地上植被调查和室内萌发试验相结合的方法,对不同放牧强度下土壤种子库的特征及其与地上植被的关系进行研究,并探讨放牧条件下地上植被、土壤种子库和土壤理化性质三者的联系,拟为高寒地区的植被恢复和草地管理提供科学参考。结果表明:1)随放牧强度的增加,土壤种子库密度呈现出“单驼峰”型趋势。2)无论是禁牧还是放牧样地,种子主要集中于0-5 cm表层土壤,且随土层的加深而减少。3)高寒草甸土壤种子库与地上植被的相似性整体较低,在中度放牧样地中杂类草占主导地位,群落物种多样性增加,相似性相对较高;在禁牧样地中种群趋于平衡且枯落层较厚,相似性最低。4)放牧干扰后,植物群落高度整体降低,地上植被盖度增加,种子库的密度增大;且较低的磷含量有利于种子的储存。综上,高寒草甸适度的放牧干扰有利于维持草地群落的物种多样性,提高种子库种子的储存,从而促进地上植被的更新建植,进而维持草地生态系统稳定。 展开更多
关键词 放牧梯度 高寒草甸 土壤种子库密度 植物功能群 物种多样性 相似性指数 土壤理化性质
下载PDF
上一页 1 2 12 下一页 到第
使用帮助 返回顶部