期刊文献+
共找到931篇文章
< 1 2 47 >
每页显示 20 50 100
Surface Water Quality Profiling Using Physicochemical Parameters in Open Defecation Free and Non-Open Defecation Free Local Government Areas in Benue State, Nigeria
1
作者 Moses T. Asoo Celestine U. Aguoru +1 位作者 Innocent O. Ogbonna Hyacinth O.A. Oluma 《Open Journal of Modern Hydrology》 CAS 2024年第3期174-191,共18页
Physicochemical parameters of surface water sources in the study of local government areas (LGAs) were assessed using standard procedures. The mean physicochemical parameters for pH (5.49), NO2 (0.23 mg/L), SO4 (0.77 ... Physicochemical parameters of surface water sources in the study of local government areas (LGAs) were assessed using standard procedures. The mean physicochemical parameters for pH (5.49), NO2 (0.23 mg/L), SO4 (0.77 mg/L), Na (28.72 mg/L), Ca (28.94 mg/L), Mg (17.50 mg/L), Cl (11.65 mg/L), TSS (6.27 mg/L), TDS (104.23 mg/L), BOD (2.83 mg/L) and F (0.87 mg/L) were below WHO standards irrespective of their defecation status. The values for electrical conductivity (EC) (2770.50 µs/cm, turbidity (481.24 NTU), dissolved oxygen (DO) (5.32 mg/L), chemical oxygen demand (COD) (445.50 mg/L), K (125.06 mg/L), PO4 (0.78 mg/L) and Fe (0.57 mg/L) were above the WHO limits for safe water. Higher EC and COD values obtained in the study is evidence of pollution of the water sources by organic matter. 展开更多
关键词 Open Defecation Surface Water Water Quality standard Physicochemical parameters
下载PDF
Analysis of the Quality of Physical and Chemical Parameters of Groundwater in Three Localities in the Sub-Prefecture of Zanzra (Ivory Coast)
2
作者 Djedjess Essoh Jules-César Meledje Bi Irié Marc Gouli +3 位作者 Drissa Ouattara Kra Vanh Eric-Simon Zran Adjourma Konate Albert Trokourey 《Journal of Materials Science and Chemical Engineering》 2024年第4期1-17,共17页
The availability of groundwater of acceptable quality has become a difficult challenge to meet in many countries, particularly Côte d’Ivoire. The State of Côte d’Ivoire and rural populations are building h... The availability of groundwater of acceptable quality has become a difficult challenge to meet in many countries, particularly Côte d’Ivoire. The State of Côte d’Ivoire and rural populations are building hydraulic infrastructure for this purpose. However, the quality of water coming from these infrastructures remains to be determined. This study therefore aims to analyze certain physicochemical parameters of the groundwater of Gloazra, Kouezra and Trahonfla. These are temperature, pH, electrical conductivity, TDS, salinity level, hardness, alkalinity, chloride content and bicarbonate. To determine the pH, electrical conductivity, temperature, TDS, and salinity rate, an electrochemical analysis was carried out. The titrimetric analysis made it possible to determine the chloride and bicarbonate content, alkalinity, and hardness. The results indicate that the studied groundwater is soft and acidic with good mineralization. This water does not present a health hazard to consumers but can affect hydraulic equipment and household containers. 展开更多
关键词 Ivory Coast Gloazra Trahonfla Kouezra Physicochemical parameters Water WHO standards
下载PDF
Optimal Microwave Radiation Field Parameters for Mercury Ion Microwave Frequency Standards 被引量:2
3
作者 Zhi-Hui Yang Hao Liu +5 位作者 Yue- Hong He Man Wang Yong-Quan Wan Yi-He Chen Lei She Jiao-Mei Li 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第6期21-24,共4页
We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experime... We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg+ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg+ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard. 展开更多
关键词 of on IT Optimal Microwave Radiation Field parameters for Mercury Ion Microwave Frequency standards DBM IS for
下载PDF
Studies on Standard Formation Enthalpies of Rare Earth Compounds by Using Structural Parameters 被引量:1
4
作者 杨锋 冯琳 《Journal of Rare Earths》 SCIE EI CAS CSCD 2000年第3期237-239,共3页
The atomic structural parameter P-i = (Z(i)*/n(i)*) (1 + n(i)*/n(i)) (1 + m(i)/Z) and the molecular structural parameter [GRAPHICS] are defined. The standard formation enthalpies (Delta(f)H(m)(phi)) of 74 species of r... The atomic structural parameter P-i = (Z(i)*/n(i)*) (1 + n(i)*/n(i)) (1 + m(i)/Z) and the molecular structural parameter [GRAPHICS] are defined. The standard formation enthalpies (Delta(f)H(m)(phi)) of 74 species of rare earth compounds were studied with P, and the correlation coefficient is R > 0.94. The structural factors and the properties of rare earth compounds are influenced by the Z(i)*, n(i)*, n(i), m(i), Z. This study has special referential value to predict the properties of rare earth compounds. 展开更多
关键词 rare earths structural parameter standard formation enthalpies
下载PDF
Effects of the Standardized Ileal Digestible Lysine to Metabolizable Energy Ratio on Performance,Nutrient Digestibility,and Plasma Parameters of 10 to 28 kg Pigs
5
作者 Pengfei Li Xiangshu Piao +5 位作者 Zhikai Zeng Ding Wang Lingfeng Xue Rongfei Zhang Bing Dong Sung Woo Kim 《Journal of Animal Science and Biotechnology》 SCIE CAS 2011年第1期35-43,共9页
A total of 480 nursery pigs (Duroc x Landrace x Large White) were utilized in two experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine (SID- Lys) to metaboliza... A total of 480 nursery pigs (Duroc x Landrace x Large White) were utilized in two experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine (SID- Lys) to metabolizable energy (ME) ratio on the performance, nutrient digestibility, plasma urea nitrogen (PUN) ,and plasma free amino acids of 10 to 28 kg pigs. In Exp. 1, 192 pigs ( 10.58 kg) were assigned to one of four treatments. The treatments consisted of diets with a ME content of 3.2, 3.25, 3.3, or 3.35 Mcal/kg with a constant SID-Lys:ME ratio of 3.7 g/Mcal. The experiment lasted 28 days. Pigs which were fed the diets containing 3.3 and 3.35 Mcal/kg ME had lower feed intakes ( P 〈 0.05)than those fed 3.2 Mcal/kg. Feed efficiency was linearly improved with increasing dietary ME ( P 〈0.05). Increasing the dietary ME level also increased (P 〈0.05 ) dry matter and energy digestibility. Therefore,3.3 Mcal/kg ME was selected for Exp. 2 in which 288 pigs ( 10.60 kg) were assigned to one of six treatments. Treatments consisted of SID-Lys: ME ratios of 3.1,3.3,3.5,3.7,3.9, or 4.1 g/Mcal with all diets providing 3.3 Mcal of ME/kg. Weight gain and feed efficiency were increased (P 〈0.05 ) as the SID-Lys:ME ratio in diet increased. Based on a straight broken-line model ,the estimated SID-Lys:ME ratio to maximize weight gain was 3.74. 展开更多
关键词 metabolizable energy nursery pigs nutrient digestibility PERFORMANCE plasma parameters standardized ileal digestible lysine
下载PDF
APPLICATION OF GEOGRAPHICAL PARAMETER DATABASE TO ESTABLISHMENT OF UNIT POPULATION DATABASE 被引量:4
6
作者 WUXi-zhi DONGChun +2 位作者 ZHAORong LIUJi-ping WANGGui-xin 《Chinese Geographical Science》 SCIE CSCD 2003年第1期34-38,共5页
Now GIS is turning into a good tool in handling geographical, economical, and population data, so we can obtain more and more information from these data. On the other hand, in some cases, for a calamity, such as hurr... Now GIS is turning into a good tool in handling geographical, economical, and population data, so we can obtain more and more information from these data. On the other hand, in some cases, for a calamity, such as hurricane, earthquake, flood, drought etc., or a decision-making, such as setting up a broadcasting transmitter, building a chemical plant etc., we have to evaluate the total population in the region influenced by a calamity or a project. In this paper, a method is put forward to evaluate the population in such special region. Through exploring the correlation of geographical parameters and the distribution of people in the same region by means of quantitative analysis and qualitative analysis, unit population database (1km× 1km) is established. In this way, estimating the number of people in a special region is capable by adding up the population in every grid involved in this region boundary. The geographical parameters are obtained from topographic database and DEM database on the scale of 1: 250 000. The fundamental geographical parameter database covering county administrative boundaries and 1km × 1km grid is set up and the population database at county level is set up as well. Both geographical parameter database and unit population database are able to oiler sufficient conditions for quantitative analysis. They will have important role in the research fields of data mining (DM), Decision-making Support Systems (DSS), and regional sustainable development. 展开更多
关键词 geographical parameter database unit population database quantitative analysis weight coefficient standardized weight coefficient
下载PDF
A New Two-Parameter Heteromorphic Elliptic Equation: Properties and Applications 被引量:5
7
作者 Zhouhu Wu 《World Journal of Engineering and Technology》 2020年第4期642-657,共16页
<div style="text-align:justify;"> The ellipse and the superellipse are both planar closed curves with a double axis of symmetry. Here we show the isoconcentration contour of the simplified two-dimensio... <div style="text-align:justify;"> The ellipse and the superellipse are both planar closed curves with a double axis of symmetry. Here we show the isoconcentration contour of the simplified two-dimensional advection-diffusion equation from a stable line source in the center of a wide river. A new two-parameter heteromorphic elliptic equation with a single axis of symmetry is defined. The values of heights, at the point of the maximum width and that of the centroid of the heteromorphic ellipse, are derived through mathematical analysis. Taking the compression coefficient <em>θ </em>= <em>b/a =</em><em></em><span></span> 1 as the criterion, the shape classification of H-type, Standard-type and W-type for heteromorphic ellipse have been given. The area formula, the perimeter theorem, and the radius of curvature of heteromorphic ellipses, and the geometric properties of the rotating body are subsequently proposed. An illustrative analysis shows that the inner contour curve of a heteromorphic elliptic tunnel has obvious advantages over the multiple- arc splicing cross section. This work demonstrates that the heteromorphic ellipses have extensive prospects of application in all categories of tunnels, liquid transport tanks, aircraft and submarines, bridges, buildings, furniture, and crafts. </div> 展开更多
关键词 Two-parameter Curve Heteromorphic Ellipse standard Equation Geometric Properties Engineering Applications
下载PDF
Effects of Complex Parameters on t→ch^0 in Supersymmetric QCD
8
作者 XINGLi-Rong MAWen-Gan ZHANGReu-You SUNYan-Bin HOUHong-Sheng 《Communications in Theoretical Physics》 SCIE CAS CSCD 2004年第2期241-246,共6页
We investigate the leading SUSY-QCD contributions to the branch ratio (BR) oft→ch~0 within the context of the minimal supersymmetric standard model (MSSM) with complex parameters,assuming more generally that there is... We investigate the leading SUSY-QCD contributions to the branch ratio (BR) oft→ch~0 within the context of the minimal supersymmetric standard model (MSSM) with complex parameters,assuming more generally that there is a misalignment between the squark and quark that leads to a flavor non-diagonal squark mass matrix.We introduce complex phases only in μ and At,namely φ_μ and φ_(Aq),for simplicity,and study the dependence of the BR of t→ch~0 on these phase parameters.Our calculations show that these CP-violation phases and the flavor mixing parameter λ influence the BR oft→ch~0 considerably,and the effect induced by φ_(At) is much larger than that by φ_μ and φ_(Ac(?)u.For different values of the complex parameters μ and A_t that are set in this paper,the BR of t -+ ch~ is in the range of 10~(-7)~10~(-6),depending mainly on the value of the trilinear coupling A_t. 展开更多
关键词 flavor changing rare decay SUSY-QCD minimal supersymmetric standard model complex parameters
下载PDF
MULTI-PARAMETER ACCELERATED MODIFIED NEWTON-RAPHSON METHODS FOR RIGIDPLASTIC FE ANALYSIS
9
作者 Shi Gang Liu Xiaolin 《Acta Mechanica Solida Sinica》 SCIE EI 2002年第4期323-331,共9页
Applications of certain multi-parameter acceleration techniques used with themodified New-ton-Raphson (mN-R) methods to solve the nonlinear equations arising from rigid-plasticfinite element analysis are investigated.... Applications of certain multi-parameter acceleration techniques used with themodified New-ton-Raphson (mN-R) methods to solve the nonlinear equations arising from rigid-plasticfinite element analysis are investigated. New modified multi-parameter techniques, developed fromCrisfield's multi-parameter methods, are utilized to solve these nonlinear equations. The numericalperformance of these techniques is compared with the standard Newton-Raphson method (sN-R),Crisfield's single parameter method (C1), Crisfield's two parameter method (C2) and Crisfield'sthree parameter method (C3). The new techniques do not involve additional residual force calculationand require little extra computational effort. In addition, they are more robust and efficient thanother existing acceleration techniques. 展开更多
关键词 rigid-plastic FEM standard newton-raphson method modified newton-raphsonmethod crisfield's multi-parameter accelerated techniques modified multi-parameter acceleratedtechniques
下载PDF
Predictive Elastoplastic Damage Constitutive Law: Establishment of Equivalence Relation between Intrinsic and Extrinsic Material Parameters
10
作者 Mohamed-Ali Rezgui Mohamed-Toumi Nasri Mahfoudh Ayadi 《Materials Sciences and Applications》 2016年第11期730-753,共24页
The purpose of the current work is the development and application of a new identification method of material parameters of elastoplastic damage constitutive model under large strains. A relationship relating the intr... The purpose of the current work is the development and application of a new identification method of material parameters of elastoplastic damage constitutive model under large strains. A relationship relating the intrinsic and extrinsic parameters of a reference material is built and transformed in equivalence relation. Extrinsic parameters concern the shape of their experimental tensile force/elongation curve, however, intrinsic parameters deal with Swift hardening law coupled with an isotropic damage variable. The relationship is carried out from a statistical characterization of a material reference (standard-steel E24). It based on multiple linear regression of a data set obtained according to a full factor design of numerical simulations of mechanical tensile tests. All materials satisfying this equivalence relation belong to the same equivalence class. This is motivated by observing that gathered materials must behave somewhat like the reference material. The material parameters can be immediately identified by only one task by running the found relationship. The current method facilitates the identification procedure and offers a substantial savings in CPU time. However it just needs only one simulation for the identification of similar behavior instead of the few hundred required when using other methods. 展开更多
关键词 Characterization parameter Identification Tensile Tests standard-Steel E24 Elastoplastic Damage Constitutive Law Equivalence Class
下载PDF
C波段双偏振天气雷达偏振参量标准差分析与改进
11
作者 张涛 张福贵 +4 位作者 潘媞 张国兴 缪应卿 余加贵 林月 《气象科技》 2024年第4期468-476,共9页
标准偏差分析方法是有效评估雷达数据质量的关键。本文采用标准差分析法对C波段双极化雷达偏振参数进行了深入分析,以找出主要影响因素并优化参数配置。通过观测实验考察了典型天气过程中极化参数标准差的改善效果。结果表明:现有观测... 标准偏差分析方法是有效评估雷达数据质量的关键。本文采用标准差分析法对C波段双极化雷达偏振参数进行了深入分析,以找出主要影响因素并优化参数配置。通过观测实验考察了典型天气过程中极化参数标准差的改善效果。结果表明:现有观测模式对C波段偏振参数的精度较低,并且不同仰角之间存在显著精度差异。其中,在1.5°仰角处,极化参数数据的精度高于0.5°仰角处。驻留时间、脉冲重复频率和脉冲数直接影响C波段双线极化雷达极化参数的标准差。通过优化脉冲重复频率和脉冲数,在不改变观测模式的情况下,提高了在相同停留时间内偏振标准差的精度。对两个典型天气过程中极化参数标准差的分析表明,在进行参数优化之前,冰雹过程中极化标准差普遍高于强降水事件;然而,在改进后,强降水事件中极化标准差精度通常优于冰雹事件。经过改进后的观测模式在一定程度上提升了C波段双极化雷达偏振参数数据的精确性。 展开更多
关键词 双偏振雷达 偏振参量 观测模式 标准差
下载PDF
基于CAPE-OPEN标准的乙苯脱氢反应器模块开发与全流程模拟
12
作者 陈旭强 江洪波 +2 位作者 杨彩娟 陈玉石 欧阳福生 《石油炼制与化工》 CAS CSCD 北大核心 2024年第9期150-157,共8页
基于某乙苯负压绝热脱氢制苯乙烯装置转化率低于设计值的现状,建立了包括小分子水蒸气转化反应在内的乙苯绝热脱氢制苯乙烯反应动力学模型和反应器模型,基于工业数据,估计了模型动力学参数,模型具有较高的精度;采用C++语言和COM技术开... 基于某乙苯负压绝热脱氢制苯乙烯装置转化率低于设计值的现状,建立了包括小分子水蒸气转化反应在内的乙苯绝热脱氢制苯乙烯反应动力学模型和反应器模型,基于工业数据,估计了模型动力学参数,模型具有较高的精度;采用C++语言和COM技术开发了符合CAPE-OPEN标准的乙苯脱氢制苯乙烯反应器单元模块;在Aspen Plus平台构建了内嵌反应器模块的乙苯脱氢制苯乙烯全流程模型,反应器与精馏塔的模拟结果与实际相吻合;进一步考察了工艺参数对装置运行中期反应的影响,提出了适宜的工艺参数,为乙苯脱氢制苯乙烯的工艺设计、生产优化提供有益的支持。 展开更多
关键词 乙苯脱氢 苯乙烯 CAPE-OPEN标准 参数估计 流程模拟
下载PDF
建立云南玉溪地区健康人群血小板生物参考区间标准研究
13
作者 王进 陈穆群 +4 位作者 白雪晶 詹学良 高翔 尹霜梅 姚昔友 《云南医药》 CAS 2024年第4期12-15,共4页
目的建立并验证云南玉溪地区健康人群外周血血小板相关参数的生物参考区间标准,为临床诊疗提供参考依据。方法回顾性分析2020年8月-2021年7月玉溪市人民医院行血常规健康体检人群的PLT计数及相关参数,建立云南玉溪地区健康人群生物参考... 目的建立并验证云南玉溪地区健康人群外周血血小板相关参数的生物参考区间标准,为临床诊疗提供参考依据。方法回顾性分析2020年8月-2021年7月玉溪市人民医院行血常规健康体检人群的PLT计数及相关参数,建立云南玉溪地区健康人群生物参考区间的新标准,对比验证新标准与原有行业标准在玉溪地区的适用性。结果云南玉溪地区PLT计数及相关参数存在性别、季节和年龄段差异,新建立的PLT参数生物参考区间标准与行业标准存在差异,差异均具有统计学意义(P<0.05)。经验证新建立的参考区间标准更能真实反映玉溪地区健康人群PLT参数状况。结论云南玉溪地区PLT计数及相关参数受性别、季节和年龄段的影响,新建立的血小板生物参考区间标准更适用于云南玉溪地区人群诊疗。 展开更多
关键词 血小板参数 生物参考区间 标准
下载PDF
基于参数标准化的单样本定标方法在微波等离子体炬水泥快速分析中的应用
14
作者 邵益波 俞登捷 +3 位作者 李雅瑞 魏好泽 金伟 于丙文 《高等学校化学学报》 SCIE EI CAS CSCD 北大核心 2024年第8期60-69,共10页
流程工业颗粒物成分的在线检测具有低延时、安全可靠及低成本等要求,目前没有适合的技术手段.微波等离子炬(Microwave plasma torch,MPT)原子发射光谱法具有直接进样、成本低及装置安全可靠等优点,有潜力成为工业在线检测的重要手段.本... 流程工业颗粒物成分的在线检测具有低延时、安全可靠及低成本等要求,目前没有适合的技术手段.微波等离子炬(Microwave plasma torch,MPT)原子发射光谱法具有直接进样、成本低及装置安全可靠等优点,有潜力成为工业在线检测的重要手段.本文基于MPT装置对水泥样品进行直接进样分析,并针对工业应用场景中标准样品受限的问题,采用单样本定标技术(Single sample calibration,SSC)进行定量分析.SSC法中的线性假设容易受到等离子体参数波动的影响,导致精度下降.为此,提出了一种基于参数标准化的SSC算法PS-SSC(SSC based on parameter standardization),通过激发温度和电子数密度对谱线强度进行修正以提高SSC的定量精度.为了评估MPT和PS-SSC方法联用在水泥成分快速分析中的有效性,将GSB 08-2985-2013标准水泥粉末气溶胶直接引入MPT中进行定量分析,并将PS-SSC与现有定量方法进行比较.与传统SSC方法相比,PS-SSC方法的决定系数R2由‒0.81~0.81提高到0.39~0.88,平均相对误差由4.39%~10.33%提高到1.55%~5.83%,平均相对标准偏差由2.89%~9.40%提高到2.28%~6.50%,展现了该方法在工业在线成分检测中的应用潜力. 展开更多
关键词 微波等离子体炬 颗粒物直接进样 单样本定标 参数标准化
下载PDF
输入基岩地震波数量对土层地震反应影响研究
15
作者 赵晶 李建亮 +1 位作者 王世元 李福海 《世界地震工程》 北大核心 2024年第3期94-102,共9页
以成都某地铁站点工程场地为例,采用一维等效线性化方法,将人工合成的不同超越概率下各20条相互独立的地震波作为基岩输入地震动时程,进行了土层地震反应计算,并对计算结果进行了分析研究,得出结论:1)通过对土层地震反应结果的计算分析... 以成都某地铁站点工程场地为例,采用一维等效线性化方法,将人工合成的不同超越概率下各20条相互独立的地震波作为基岩输入地震动时程,进行了土层地震反应计算,并对计算结果进行了分析研究,得出结论:1)通过对土层地震反应结果的计算分析,给出了PGA、T_(g)和S_(a)(T)值计算结果参数的变异系数和随概率档的变化规律,并验证了上述各参数均值都服从正态分布。2)对于Ⅱ级和地震小区划工作,目前业内较为普遍地采用3条基岩地震波作为土层地震反应计算基岩输入地震动时程的做法和现行地震安评国标的规定,至少采用3条基岩地震波作为输入地震动时程下限数量的规定已不能满足要求,需要增加,建议增加到最少采用15条基岩输入地震波,以保证地震安评工作所提供的场地设计地震动参数更加可靠。 展开更多
关键词 输入地震动时程 样本数量 地震动参数 离散性 国标下限
下载PDF
障碍物特性曲线参数反演及车辆碰撞性评估
16
作者 毕妤靖 秦睿贤 陈秉智 《铁道标准设计》 北大核心 2024年第9期208-215,共8页
城市有轨电车多采用混合路权,即有轨电车与地面交通车辆、行人等共享路权。由于运营的特殊性,有轨电车发生碰撞事故概率较大,对其被动安全防护研究具有重要意义。EN 15227—2020标准针对C-IV类有轨电车增加了城市道路交通7.5 t障碍物碰... 城市有轨电车多采用混合路权,即有轨电车与地面交通车辆、行人等共享路权。由于运营的特殊性,有轨电车发生碰撞事故概率较大,对其被动安全防护研究具有重要意义。EN 15227—2020标准针对C-IV类有轨电车增加了城市道路交通7.5 t障碍物碰撞工况,为得到符合标准的障碍物模型,对障碍物特性曲线进行参数反演,并应用符合标准的障碍物对车辆耐撞性进行评估。首先应用Hyper-Mesh软件建立城市道路交通7.5t障碍物有限元模型;然后应用Isight集成Pam-Crash软件对材料弹性模量及应力-应变曲线进行参数反演,得到符合标准的障碍物特性曲线;最后分别将障碍物标准曲线缩放至0.75及1.25倍,分析3种不同标准曲线下障碍物模型对有轨电车耐撞性评估的影响。结果表明:参数反演后得到的障碍物模型符合标准要求,可较好地对车辆耐撞性进行评估。相比于1.0倍标准曲线的障碍物模型,采用1.25倍标准曲线的障碍物模型,碰撞后障碍物吸能减少10.9%,撞击时冲击力峰值增加34.4%,列车司机室生存空间压缩量增大9.1%,1.25倍标准曲线下列车耐撞性指标偏保守;采用0.75倍标准曲线的障碍物模型,碰撞后障碍物吸能增加24.9%,撞击时冲击力峰值减少6.5%,列车司机室生存空间压缩量减少39.3%,0.75倍标准曲线下列车耐撞性指标偏高。 展开更多
关键词 有轨电车 参数反演 障碍物 碰撞 EN15227-2020标准
下载PDF
明渠非标准断面法测流水位流量关系的率定及影响因素分析
17
作者 梁慧真 宗全利 +2 位作者 刘贞姬 谢炎 刘冬冬 《排灌机械工程学报》 CSCD 北大核心 2024年第2期147-153,160,共8页
为探究明渠非标准断面法测流的水位流量关系曲线的率定问题,以新疆第三师某团场25处渠道量水断面为研究对象,利用FlowTracker 2手持式声学多普勒流速仪进行了水位流量关系率定工作.根据实测结果,率定了各渠道量水断面的水位流量关系曲线... 为探究明渠非标准断面法测流的水位流量关系曲线的率定问题,以新疆第三师某团场25处渠道量水断面为研究对象,利用FlowTracker 2手持式声学多普勒流速仪进行了水位流量关系率定工作.根据实测结果,率定了各渠道量水断面的水位流量关系曲线,并对所率定出的曲线进行了符号检验、适线检验和偏离数值检验及误差分析,在此基础上,对流量拟合参数的影响因素进行了分析.结果表明:所率定的25处渠道量水断面中,14处具有稳定的水位流量关系,5处受回水影响、6处受渠道淤积影响为不稳定的水位流量关系;在渠道粗糙系数Ra、边坡系数m及坡降i相同的条件下,流量拟合参数与渠道底宽b总体上呈正相关;在渠道粗糙系数Ra、边坡系数m及底宽b相同的条件下,流量拟合参数与渠道坡降i总体上呈负相关.研究结果可以为灌区自动化量水设备测流准确性的校核提供参考依据. 展开更多
关键词 非标准断面法 水位流量关系曲线 率定 流量拟合参数 自动化量水
下载PDF
白附子标准汤剂的物性参数与化学成分相关性研究
18
作者 史可 王春燕 +2 位作者 位玉蝶 马彦江 陈天朝 《中华中医药学刊》 CAS 北大核心 2024年第6期146-153,共8页
目的 探究白附子标准汤剂的物性参数与其化学成分之间的相关性并建立模型,以期用物性参数指征内在化学成分,为实现标准汤剂的快速质量评价提供参考。方法 制备白附子生品及炮制品的标准汤剂,测定其物性参数(相对密度、pH值、氧化值),紫... 目的 探究白附子标准汤剂的物性参数与其化学成分之间的相关性并建立模型,以期用物性参数指征内在化学成分,为实现标准汤剂的快速质量评价提供参考。方法 制备白附子生品及炮制品的标准汤剂,测定其物性参数(相对密度、pH值、氧化值),紫外分光光度法测定淀粉、总多糖、总黄酮的含量,高效液相色谱法测定核苷类成分及有机酸类成分的含量,采用熵权TOPSIS客观赋权法建立多指标综合评分,利用SPSS 21.0软件对白附子标准汤剂的物性参数、化学成分及综合评分进行相关性分析,并建立相应的回归模型。结果 相关性分析显示白附子标准汤剂物性参数与化学成分呈显著相关,其中pH值和相对密度是与内在化学成分最为关联的两个物性参数;综合评分与相对密度呈显著负相关,与pH值、氧化值均呈显著正相关;回归分析所建立的模型,拟合度均较高,模型有效。结论 研究对白附子标准汤剂的物性参数和大、小分子成分含量进行综合考察,其物性参数与化学成分呈显著相关,建立的回归模型拟合度均较高,表明以物性参数指征内在化学成分具有可行性,可为实现白附子标准汤剂的快速质量评价与控制提供一定的参考依据。 展开更多
关键词 白附子 标准汤剂 物性参数 化学成分 熵权TOPSIS法 相关性
下载PDF
多参数磁共振成像联合LI-RADS分级标准对肝硬化再生结节与小肝癌的诊断价值及临床意义
19
作者 蔡宁 石惠 +1 位作者 李真真 郭君武 《中国医科大学学报》 CAS 北大核心 2024年第8期686-691,共6页
目的探讨多参数磁共振成像(Mp-MRI)联合肝脏影像报告和数据管理系统(LI-RADS)分级标准对肝硬化再生结节与小肝癌(SHCC)的诊断价值及临床意义。方法选取2019年3月至2023年3月我院直径≤3 cm的肝脏结节患者86例(132个结节),根据手术病理... 目的探讨多参数磁共振成像(Mp-MRI)联合肝脏影像报告和数据管理系统(LI-RADS)分级标准对肝硬化再生结节与小肝癌(SHCC)的诊断价值及临床意义。方法选取2019年3月至2023年3月我院直径≤3 cm的肝脏结节患者86例(132个结节),根据手术病理结果将肝硬化再生结节38例(54个结节)记为良性组,SHCC 48例(78个结节)记为恶性组。比较2组LI-RADS分级和Mp-MRI参数[增强率(ER)、平均强化时间(MET)、最大上升斜率(MSI)、最大下降斜率(MSD)、表观扩散系数(ADC)、脂肪分数(FF)],分析其诊断价值。结果经LI-RADS分级标准诊断,132个结节中共检出阳性76个,阴性56个,其中假阳性10个,假阴性12个;恶性组ER、MET、MSI、ADC低于良性组,FF、MSD高于良性组(P<0.05);受试者操作特征(ROC)曲线分析结果显示,Mp-MRI参数联合LI-RADS分级标准诊断肝硬化再生结节与SHCC的曲线下面积(AUC)为0.946(95%CI:0.892~0.977),约登指数为0.811,灵敏度为88.46%,特异度为92.59%,优于各Mp-MRI参数及LI-RADS分级单独诊断;恶性组不同病理分级结节LI-RADS分级比较,差异有统计学意义(P<0.05);ER、MET、MSI、ADC在高分化结节中最高,中分化结节次之,低分化结节最低,FF、MSD在低分化结节最高,中分化结节次之,高分化结节最低(P<0.05);Spearman相关性分析结果显示,LI-RADS分级、ER、MET、MSI、ADC与SHCC病理分级呈正相关,FF、MSD与SHCC病理分级呈负相关(P<0.05)。结论Mp-MRI参数联合LI-RADS分级标准诊断肝硬化再生结节与SHCC的价值可靠,且能为临床评估SHCC病理分级提供参考依据。 展开更多
关键词 肝硬化再生结节 小肝癌 多参数磁共振成像 肝脏影像报告和数据管理系统分级标准 诊断价值
下载PDF
黄土标贯击数与物理力学参数相关性及微观机制分析
20
作者 荣誉 倪万魁 +3 位作者 聂永鹏 任思远 陈家乐 拓文鑫 《科学技术与工程》 北大核心 2024年第3期1192-1199,共8页
为了补充西安市黄土塬区利用标贯击数预测土的物理力学参数的方法,以西安市长安区黄土塬地基土为例,通过现场标贯试验和室内土工试验,对地基土的标贯击数值与物理力学参数进行了一元和多元相关性分析,给出了拟合关系式及其相关系数;并... 为了补充西安市黄土塬区利用标贯击数预测土的物理力学参数的方法,以西安市长安区黄土塬地基土为例,通过现场标贯试验和室内土工试验,对地基土的标贯击数值与物理力学参数进行了一元和多元相关性分析,给出了拟合关系式及其相关系数;并利用电镜扫描及PCAS图像处理技术,从黄土微观结构角度对研究结果做了进一步分析。结果表明:黄土塬地基土的含水率、干密度、孔隙比、液限、黏聚力、内摩擦角、压缩系数均与标贯击数N有很好的线性相关性,地基土的湿陷系数与标贯击数N的线性相关性良好,可用N值对地基土的物理力学参数进行预测。研究成果可为西安黄土塬区岩土工程勘察提供参考。 展开更多
关键词 西安黄土塬 土的物理力学参数 标准贯入 相关性 微观结构
下载PDF
上一页 1 2 47 下一页 到第
使用帮助 返回顶部