期刊文献+
共找到1,522篇文章
< 1 2 77 >
每页显示 20 50 100
Micro-macro Unified Analysis of Flow Behavior of Particle-reinforced Metal Matrix Composites 被引量:2
1
作者 张鹏 李付国 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2010年第2期252-259,共8页
This article presents a micro-macro unified model for predicting the deformation of metal matrix composites (MMCs). A macro-scale model is developed to obtain the proper boundary conditions for the micro-scale model... This article presents a micro-macro unified model for predicting the deformation of metal matrix composites (MMCs). A macro-scale model is developed to obtain the proper boundary conditions for the micro-scale model, which is used to assess the microstructural deformation of materials. The usage of the submodel technique in the analysis makes it possible to shed light on the stress and strain field at the microlevel. This is helpful to investigate the linkage between the microscopic and the macroscopic flow behavior of the composites. An iterative procedure is also proposed to find out the optimum parameters. The results show that the convergence can be attained after three iterations in computation. In order to demonstrate the reliability of mi- cro-macro unified model, results based on the continuum composite model are also investigated using the stress-strain relation of composite obtained from the iterations. By comparing the proposed unified model to the continuum composite model, it is clear that the former exhibits large plastic deformation in the case of little macroscopic deformation, and the stresses and strains obtained from the submodel are higher than those from the macroscopic deformation. 展开更多
关键词 metal matrix composites micro-macro unified model submodel flow behavior microSTRUCTURE
原文传递
The Influence of Macro and Micro Contexts on Teaching and Learning in the Classroom
2
作者 叶译 《海外英语》 2014年第9X期23-28,共6页
This paper is based on three observations and independent thinking of the classroom teaching of the author’s colleagues.It attempts to examine how macro and micro contexts affect teaching and learning in the classroo... This paper is based on three observations and independent thinking of the classroom teaching of the author’s colleagues.It attempts to examine how macro and micro contexts affect teaching and learning in the classroom.The author focuses the discussion on three aspects:(i)the present EFL contextual setting in China;(ii)the influence of the evaluation system on both teachers and students;(iii)his own beliefs as a teacher.Finally,he comes to the implications that teachers should often reflect on their teaching by means of observing other teachers’teachings;In order to bring more effective teaching and learning to the class,Teachers should change their class from a teacher-centered one to a students-centered one. 展开更多
关键词 influence macro CONTEXT micro CONTEXT teaching and
在线阅读 下载PDF
Macro-and Micro-Properties of Two Natural Marine Clays in China 被引量:7
3
作者 蒋明镜 彭立才 +2 位作者 朱合华 林奕禧 黄良机 《China Ocean Engineering》 SCIE EI 2009年第2期329-344,共16页
In this paper,macro-and micro-properties of natural marine clay in two different and representative regions of China are investigated in detail.In addition to in-situ tests,soil samples are collected by use of Shelby ... In this paper,macro-and micro-properties of natural marine clay in two different and representative regions of China are investigated in detail.In addition to in-situ tests,soil samples are collected by use of Shelby tubes for laboratory examination in Shanghai and Zhuhai respectively,two coastal cities in China.In the laboratory tests,macro-properties such as consolidation characteristics and undrained shear strength are measured.Moreover,X-ray diffraction test,scanning electron microscope test,and mercury intrusion test are carried out for the investigation of their micro-properties including clay minerals and microstructure.The study shows that:(1)both clays are Holocene series formations,classified as either normal or underconsolidated soils.The initial gradient of the stress-strain curves shows their increase with increasing consolidation pressure;however,the Shanghai and the Zhuhai clays are both structural soils with the latter shown to be more structured than the former.As a result,the Zhuhai clay shows strain softening behavior at low confining pressures,but strain hardening at high pressures.In contrast,the Shanghai clay mainly manifests strain-hardening.(2)An activity ranges from 0.75 to 1.30 for the Shanghai marine clay and from 0.5 to 0.85 for the Zhuhai marine clay.The main clay mineral is illite in the Shanghai clay and kaolinite in the Zhuhai clay.The Zhuhai clay is mainly characterized by a flocculated structure,while the typical Shanghai clay shows a dispersed structure.The porous structure of the Shanghai clay is characterized mainly by large and medium-sized pores,while the Zhuhai clay porous structure is mainly featured by small and medium-sized pores.The differences in their macro-and micro-properties can be attributed to different sedimentation environments. 展开更多
关键词 marine clay macro- and micro- properties comparison microSTRUCTURE
在线阅读 下载PDF
Numerical Simulation of Macro-and Micro-structures of Intense Convective Clouds with a Spectral Bin Microphysics Model 被引量:4
4
作者 刘晓莉 牛生杰 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第5期1078-1088,共11页
By use of a three-dimensional compressible non-hydrostatic convective cloud model with detailed microphysics featuring spectral bins of cloud condensation nuclei (CCN), liquid droplets, ice crystals, snow and graupe... By use of a three-dimensional compressible non-hydrostatic convective cloud model with detailed microphysics featuring spectral bins of cloud condensation nuclei (CCN), liquid droplets, ice crystals, snow and graupel particles, the spatial and temporal distributions of hydrometeors in a supercell observed by the (Severe Thunderstorm Electrification and Precipitation Study) STEPS triple-radar network are simulated and analyzed. The bin model is also employed to study the effect of CCN concentration on the evolution characteristics of the supercell. It is found that the CCN concentration not only affects the concentration and spectral distribution of water droplets, but also influences the characteristics of ice crystals and graupel particles. With a larger number of CCN, more water droplets and ice crystals are produced and the growth of graupel is restrained. With a small quantity of CCN the production of large size water droplets are promoted by initially small concentrations of water droplets and ice crystals, leading to earlier formation of small size graupel and restraining the recycling growth of graupel, and thus inhibiting the formation of large size graupel (or small size hail). It can be concluded that both the macroscopic airflow and microphysical processes influence the formation and growth of large size graupel (or small size hail). In regions with heavy pollution, a high concentration of CCN may restrain the formation of graupel and hail, and in extremely clean regions, excessively low concentrations of CCN may also limit the formation of large size graupel (hail). 展开更多
关键词 spectral bin microphysics macro-micro structures concentration of CCN
在线阅读 下载PDF
Recent Advances in Computational Simulation of Macro-,Meso-,and Micro-Scale Biomimetics Related Fluid Flow Problems 被引量:5
5
作者 Y. Y. Yan 《Journal of Bionic Engineering》 SCIE EI CSCD 2007年第2期97-107,共11页
Over the last decade, computational methods have been intensively applied to a variety of scientific researches and engineering designs. Although the computational fluid dynamics (CFD) method has played a dominant r... Over the last decade, computational methods have been intensively applied to a variety of scientific researches and engineering designs. Although the computational fluid dynamics (CFD) method has played a dominant role in studying and simulating transport phenomena involving fluid flow and heat and mass transfers, in recent years, other numerical methods for the simulations at meso- and micro-scales have also been actively applied to solve the physics of complex flow and fluid-interface interactions. This paper presents a review of recent advances in multi-scale computational simulation of biomimetics related fluid flow problems. The state-of-the-art numerical techniques, such as lattice Boltzmann method (LBM), molecular dynamics (MD), and conventional CFD, applied to different problems such as fish flow, electro-osmosis effect of earthworm motion, and self-cleaning hydrophobic surface, and the numerical approaches are introduced. The new challenging of modelling biomimetics problems in developing the physical conditions of self-clean hydrophobic surfaces is discussed. 展开更多
关键词 biomimetics computational simulation macro- meso- micro-SCALE HYDROPHOBIC SURFACES
在线阅读 下载PDF
Research on failure criterion of composite based on unified macro- and micro-mechanical model 被引量:6
6
作者 Sun Zhigang Zhao Long +1 位作者 Chen Lei Song Yingdong 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2013年第1期122-129,共8页
A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress di... A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress distribution of composite structure was calculated by commercial finite element analysis software. According to the macro stress distribution, the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics (FVDAM), which was a multi-scale finite element method for composite. The micro structure failure modes were estimated with the failure strength of constituents. A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro- and micro-mechanics failure analysis method. The results obtained by the two methods are consistent, which show this new method's accuracy and efficiency. 展开更多
关键词 COMPOSITE Finite-volume direct averaging micromechanics Mechanics failure model Multi-scale finite element Unified macro and micro
原文传递
A REVIEW ON RESEARCH ON DEVELOPMENT OF LIGAMENT CONSTITUTIVE RELATIONS ON MACRO, MESO, AND MICRO LEVELS 被引量:1
7
作者 Chao Wan Zhixiu Hao Shizhu Wen 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2013年第4期331-343,共13页
Ligaments are densely connective soft tissues capable of maintaining stability and function of knee joint.As an important factor,the constitutive relation of ligament would affect its biomechanics and further play an ... Ligaments are densely connective soft tissues capable of maintaining stability and function of knee joint.As an important factor,the constitutive relation of ligament would affect its biomechanics and further play an essential role in the research on ligament injury,healing and treatment.The objective of this paper is to provide an overview of the current research on ligament constitutive relations on the macro,meso,and micro levels as well as the anatomy and histological structure of ligament.Some studies of biomechanical behaviors during ligament injury and healing periods have also been investigated.Based on the research on ligament constitutive relation in the past three decades,a discussion of some research perspectives is also presented,such as a validated accurate measuring method of in situ strain in ligament,a new constitutive relation involving the distribution of ultra-structural properties,and a rational estimation of ligament injury and healing process by the change of its ultra-structural or histological characteristics. 展开更多
关键词 constitutive relation LIGAMENT ULTRA-STRUCTURE macro MESO micro
原文传递
Sedimentary Micro-facies and Macro Heterogeneity of Reservoir Beds in the Third Member of the Qingshankou Formation,Qian'an Area,Songliao Basin 被引量:4
8
作者 SHAN Xuanlong HU Jinxiang +1 位作者 Reinhard F. SACHSENHOFER SHI Tiaotiao 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2007年第6期1033-1040,共8页
An analysis of drill cores and well logs shows that the main micro-facies of the third member sand bodies of the Qingshankou Formation in Qian'an are subaqueous distributary channel facies, sheet sand facies and suba... An analysis of drill cores and well logs shows that the main micro-facies of the third member sand bodies of the Qingshankou Formation in Qian'an are subaqueous distributary channel facies, sheet sand facies and subaqueous fan facies (olistostrome). Maps showing the distribution of these micro-facies together with inter-channel bay and prodelta mocro-facies are presented for different time-slices (lower, middle and upper parts of the Qingshankou Formation). These maps reveal the instability and change of sediment transport in the Baokang sedimentary system during the depositional period. Sediment transport was from the west in the early stage, from the south in the middle stage and from the northwest in the late stage. Values of thickness, porosity and permeability of the sand bodies in the third member of the Qingshankou Formation show that they have low to medium porosity and low permeability, and are characterized by serious reservoir heterogeneity. The joints between micro-facies and subaqueous fan micro-facies are characterized by the highest heterogeneity, the sheet sand and distal sand bar subfacies come next, and the heterogeneity of the subaqueous distributary channel sand bodies is relatively weak. 展开更多
关键词 Songliao Basin Qingshankou Formation sedimentary micro-facies macro heterogeneity of reservoir beds
在线阅读 下载PDF
A Fractional Micro-Macro Model for Crowds of Pedestrians Based on Fractional Mean Field Games 被引量:1
9
作者 Kecai Cao Yang Quan Chen Daniel Stuart 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI 2016年第3期261-270,共10页
Modeling a crowd of pedestrians has been considered in this paper from different aspects. Based on fractional microscopic model that may be much more close to reality, a fractional macroscopic model has been proposed ... Modeling a crowd of pedestrians has been considered in this paper from different aspects. Based on fractional microscopic model that may be much more close to reality, a fractional macroscopic model has been proposed using conservation law of mass. Then in order to characterize the competitive and cooperative interactions among pedestrians, fractional mean field games are utilized in the modeling problem when the number of pedestrians goes to infinity and fractional dynamic model composed of fractional backward and fractional forward equations are constructed in macro scale. Fractional micromacro model for crowds of pedestrians are obtained in the end. Simulation results are also included to illustrate the proposed fractional microscopic model and fractional macroscopic model, respectively. © 2014 Chinese Association of Automation. 展开更多
关键词 Control systems Electrical engineering
在线阅读 下载PDF
Power Supply of Macro-Micro Driven Linear Piezoelectric Motor
10
作者 Zhang Tiemin Liao Yiyong +2 位作者 Xu Zhilin Liang Li Cao Fei 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2017年第1期22-29,共8页
To investigate a novel macro and micro driven linear piezoelectric motor composed of an ultrasonic motor with macro movement and a piezoelectric actuator with micro movement,a digital signal processing(DSP)based macro... To investigate a novel macro and micro driven linear piezoelectric motor composed of an ultrasonic motor with macro movement and a piezoelectric actuator with micro movement,a digital signal processing(DSP)based macro and micro power supply is designed,which fits the new linear piezoelectric motor.The power supply comprises a control circuit,a voltage conversion circuit,an amplifier circuit,a half-bridge module,an optical isolatorsdrive circuit,etc,where the DSP of TMS320F28335 is used as the controller.When the linear piezoelectric motor working in a macro driven state,the power supply outputs alternating currents with high frequency and high voltage,which drives the linear piezoelectric motor dynamically at an ultrasonic frequency;while working in the micro driven state,the power supply outputs direct currents with high voltage,which drives the linear piezoelectric motor in micro driven statically.Here a prototype of the macro-micro power supply is designed.After a series of experiments on the power supply with and without loads,the results show that the power supply can drive and control the macro micro driven linear piezoelectric motor,and realizes quick and seamless switch between macro and micro drive.In addition,the power supply can drive and control the ultrasonic motor or piezoelectric ceramic micro actuator individually.The power supply achieves the multiple parameters of output signals adjustable simultaneously and exhibits good control characteristics. 展开更多
关键词 LINEAR piezoelectric motor macro-micro drive DSP half-bridge module
在线阅读 下载PDF
Complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities
11
作者 Zhen Li Yu Han Le-Man Kuang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2020年第2期30-37,共8页
We theoretically study complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities.We investigate quantum dynamics of micro-micro and micro-macro entangl... We theoretically study complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities.We investigate quantum dynamics of micro-micro and micro-macro entanglement in the micro-macro system.It is found that strong micro-macro entanglement between Rydberg impurities and the BEC can be generated by the use of initial micro-micro entanglement between two Rydberg impurities,which acts as the seed entanglement to create micro-macro entanglement.We demonstrate a curious complementarity relation between micro-micro and micro-macro entanglement,and find that the complementarity property can be sustained to some extent even though in the presence of the BEC decoherence. 展开更多
关键词 complementarity micro-macro ENTANGLEMENT micro-micro ENTANGLEMENT a BOSE-EINSTEIN CONDENSATE RYDBERG IMPURITIES
原文传递
Macro-Micro-Anatomy of the Lingual Artery
12
作者 吴海燕 何光篪 陈尔瑜 《Journal of Medical Colleges of PLA(China)》 CAS 1990年第3期300-305,共6页
The macro-micro-anatomy of the lingual artery of 25 adult cadavers wasstudied.The origin of the artery is rather concentrated and the greater cornu of thehyoid bone can be used as the indicator.The entrance of the art... The macro-micro-anatomy of the lingual artery of 25 adult cadavers wasstudied.The origin of the artery is rather concentrated and the greater cornu of thehyoid bone can be used as the indicator.The entrance of the artery into the hyoglossusmuscle is almost constantly along the posterior border of the muscle,where the artery issuperficially located and easily to be exposed,and has a constant relationship with thevein and hypoglossal nerve.Thus the lingual artery can be used as the artery of a recipientarea in case of tongue reconstruction.The deep lingual artery has two types ofbranches;the short ones mainly supply the muscles of tongue while the long ones mainlysupply the mucosa by forming a submucosal network.In the muscles of tongue,minutearterioles run tortuously along the muscular fibers with abundant anastomoses betweeneach other,but no anastomosis is found to cross over the rnidline of the tongue.Be-neath the mucosa,there is an arterial network spreading all over the whole tongue notlimited to one side.The relationship of the arterial architecture to the structure and thefunctions of the tongue and its clinical significance were discussed. 展开更多
关键词 LINGUAL ARTERY deep LINGUAL ARTERY sublinguat ARTERY ARTERIAL architecture macro-micro-anatomy
暂未订购
基于定位误差补偿的亚微米级宏微驱动系统设计与试验
13
作者 杨满芝 刘嘉豪 +3 位作者 张传伟 桂皓晨 李林岳 冯斌 《农业机械学报》 北大核心 2026年第1期404-412,共9页
为解决传统机械系统在大范围运动中高精度定位问题,本文设计了一种精密宏微驱动系统,通过微驱动系统补偿宏驱动系统定位误差,实现亚微米级精密定位。基于柔性铰链杠杆原理和平衡附加力原理,设计了一种微动放大机构,可将输入位移按设计... 为解决传统机械系统在大范围运动中高精度定位问题,本文设计了一种精密宏微驱动系统,通过微驱动系统补偿宏驱动系统定位误差,实现亚微米级精密定位。基于柔性铰链杠杆原理和平衡附加力原理,设计了一种微动放大机构,可将输入位移按设计放大比1.5精密放大且无附加位移。在宏微驱动系统中,伺服电机和滚珠丝杠结合作为宏驱动系统,采用压电陶瓷制动器驱动微动放大机构作为微驱动系统,并用以补偿宏驱动系统的定位误差,实现大行程高精度运动。在完成宏微驱动系统工作原理设计的基础上,分析系统定位误差并提出误差补偿方案,开展宏微驱动系统定位误差补偿试验。试验结果显示:在运动行程2 mm范围内,经过定位误差补偿后,宏微驱动系统的平均定位误差由14.49μm降低至0.34μm,平均定位误差降低97.65%。定位误差补偿试验验证了宏微驱动系统设计及误差补偿方案的有效性与精确性。 展开更多
关键词 宏微驱动系统 定位误差补偿 微动机构 柔性铰链
在线阅读 下载PDF
黏土基泡沫聚合土路基材料的保温性能及力学特性
14
作者 赵阳 卢正 +4 位作者 刘杰 张荣 颜廷舟 唐楚轩 李剑 《中国科学院大学学报(中英文)》 北大核心 2026年第1期51-60,共10页
以乌鲁木齐绕城高速沿线的挖方弃土为基础,结合水泥和泡沫,共同研发具有多孔保温特性的泡沫聚合土。系统探讨湿密度、土壤掺量和水料比对泡沫聚合土导热性能、无侧限抗压强度和刚度的影响,建立孔隙结构与宏观性能之间的内在联系。研究... 以乌鲁木齐绕城高速沿线的挖方弃土为基础,结合水泥和泡沫,共同研发具有多孔保温特性的泡沫聚合土。系统探讨湿密度、土壤掺量和水料比对泡沫聚合土导热性能、无侧限抗压强度和刚度的影响,建立孔隙结构与宏观性能之间的内在联系。研究结果表明,当泡沫聚合土的密度从600 kg/m^(3)提升至1200 kg/m^(3)时,其导热系数增长约1倍,强度增强约3.95倍,模量更是增长约10.5倍。相较于传统的路基土,泡沫聚合土的导热系数显著降低52%~96.4%。进一步对孔隙结构进行分析,发现随着单位体积内泡沫聚合土孔径的减小,骨架占比相应增加,气孔体积则有所减少。这种细观结构的变化在宏观性能上表现为保温性能的提升(即导热系数的降低)以及力学性能的显著增强(包括强度和刚度的提升)。泡沫聚合土不仅展现出较好的保温性能,还具备较强的力学特性,为季冻区路基的防寒保温层提供了合适的解决方案。 展开更多
关键词 泡沫聚合土 导热系数 力学性能 宏细观相关性
在线阅读 下载PDF
同轴集成式宏微复合驱动器的驱动力和微动位移优化研究
15
作者 喻曹丰 王宁 +2 位作者 张奇龙 杨坤 魏益军 《机电工程》 北大核心 2026年第1期149-158,共10页
精密定位与驱动技术是实现高精度加工的关键基础。通过优化同轴集成式宏微复合驱动器的结构,提高其宏微复合驱动器(MMCA)驱动力与微动位移的工作性能,可以实现高速大行程运动与纳米级定位精度的协同输出目的。为了解决同轴集成式宏微复... 精密定位与驱动技术是实现高精度加工的关键基础。通过优化同轴集成式宏微复合驱动器的结构,提高其宏微复合驱动器(MMCA)驱动力与微动位移的工作性能,可以实现高速大行程运动与纳米级定位精度的协同输出目的。为了解决同轴集成式宏微复合驱动器(MMCA)工作性能低下的问题,对MMCA的永磁体和微动线圈结构进行了优化研究。首先,以MMCA的驱动力为目标函数,以提高宏动线圈上产生的磁通密度模和波动幅度为评判标准,优化了永磁体结构;然后,提出了六段变半径的微动线圈的设计方法,以超磁致伸缩材料(GMM)的伸长量为目标函数,以微动线圈在GMM棒上产生的磁通密度模为评价指标,优化了微动线圈各段的最佳半径;最后,基于仿真优化参数搭建了实验平台,对MMCA驱动力与微动位移的性能提升进行了验证。研究结果表明:将永磁体梯度优化为1.5 mm、弧度半径为1350 mm,在6 A宏动线圈电流下实现了191.2 N的优化驱动力目标,驱动力性能提高了36.6%;同时,采用六段变半径分别为15 mm、13 mm、10 mm、9 mm、9 mm、10 mm的微动线圈设计,将微动位移从57.5μm提升至74.4μm,微动位移性能提高了29.4%。宏微驱动性能的显著提升,表明了该优化方法的有效性,可以为宏微复合驱动器设计优化提供一种方案。 展开更多
关键词 超精密加工 超精密定位与驱动技术 磁通密度模 宏微复合驱动器 微动线圈 宏动结构和微动结构 超磁致伸缩材料
在线阅读 下载PDF
非线性载荷作用下岩石高效破碎的研究进展
16
作者 赵环帅 潘永泰 +3 位作者 曹行健 赵英嘉 余超 乔鑫 《北京大学学报(自然科学版)》 北大核心 2026年第1期198-208,共11页
结合国内外发展现状,分析开展岩石高效破碎理论与技术研究的必要性,介绍非线性载荷在岩石破碎中的主要优势,从非线性压缩加载(单轴压缩、巴西劈裂和点载荷)、冲击加载(应力波、机械冲击和高压电脉冲)和振动加载3个方面,系统分析非线性... 结合国内外发展现状,分析开展岩石高效破碎理论与技术研究的必要性,介绍非线性载荷在岩石破碎中的主要优势,从非线性压缩加载(单轴压缩、巴西劈裂和点载荷)、冲击加载(应力波、机械冲击和高压电脉冲)和振动加载3个方面,系统分析非线性载荷下岩石破碎方面的研究进展,阐述不同加载方式下破岩的优缺点。针对目前非线性载荷下岩石破碎研究中存在的问题,提出岩石力学模型构建、宏-细-微观多尺度探索、加载方式复合、能量测试与计算以及智能技术应用等未来的重点研究方向。 展开更多
关键词 岩石破碎 非线性载荷 力学模型 宏-细-微观多尺度 加载方式复合 能量计算 智能技术
在线阅读 下载PDF
Chemical analysis,antimicrobial and anti-oxidative properties of Daucus gracilis essential oil and its mechanism of action 被引量:2
17
作者 Meriem El Kolli Hocine Laouer +2 位作者 Hayet El Kolli Salah Akkal Farida Sahli 《Asian Pacific Journal of Tropical Biomedicine》 SCIE CAS 2016年第1期8-15,共8页
Objective:To evaluate the essential oils(EO) composition,antimicrobial and antioxidant power of a local plant,Daucus gracilis(D.gracilis).Methods:The aerial parts of D.gracilis were subjected to hydro distillation by ... Objective:To evaluate the essential oils(EO) composition,antimicrobial and antioxidant power of a local plant,Daucus gracilis(D.gracilis).Methods:The aerial parts of D.gracilis were subjected to hydro distillation by a Clevenger apparatus type to obtain the EO which had been analyzed by gas chromatography and gas chromatography coupled with mass spectrometry,and screened for antimicrobial activity against five bacteria and three fungi by agar diffusion method.The mechanism of action of the EO was determined on the susceptible strains by both of time kill assay and lysis experience.The minimal inhibitory concentrations were determined by agar macrodilution and micro-dilution methods.Anti-oxidative properties of the EO were also studied by free diphenyl-2-picrylhydrazyl radical scavenging and reducing power techniques.Results:The EO yielded 0.68(v/w).The chemical analysis presented two dominant constituents which were the elemicin(35.3%) and the geranyl acetate(26.8%).D.gracilis EO inhibited the growth of Bacillus cereus and Proteus mirabilis significantly with minimal inhibitory concentrations of 17.15 μg/mL by the agar dilution method and57.05 μg/mL and 114.1 μg/mL,respectively by liquid micro-dilution.A remarkable decrease in a survival rate as well as in the absorbance in 260 nm was recorded,which suggested that the cytoplasm membrane was one of the targets of the EO.The EO showed,also,important anti-oxidative effects with an IC50 of 0.002 mg/mL and a dosedependent reducing power.Conclusions:D.gracilis EO showed potent antimicrobial and anti-oxidative activities and had acted on the cytoplasm membrane.These activities could be exploited in the food industry for food preservation. 展开更多
关键词 DAUCUS GRACILIS Apiaceae Essential OILS ANTImicroBIAL ACTIVITY macro-dilution micro-dilution Anti-oxidative ACTIVITY Reducing power
暂未订购
基于声发射和离散元理论煤体宏细观损伤力学行为研究 被引量:1
18
作者 张琪 李祥春 +1 位作者 刘耀儒 聂百胜 《中南大学学报(自然科学版)》 北大核心 2025年第1期173-188,共16页
研究煤体在加载过程中的宏细观尺度损伤力学行为对于从本质上探寻连续-非连续型材料的损伤破坏机理至关重要。本文基于声发射监测实验并结合PFC2D离散元软件,从本质上阐述煤体材料复杂宏观力学行为的细观损伤破坏机理。研究结果表明:当... 研究煤体在加载过程中的宏细观尺度损伤力学行为对于从本质上探寻连续-非连续型材料的损伤破坏机理至关重要。本文基于声发射监测实验并结合PFC2D离散元软件,从本质上阐述煤体材料复杂宏观力学行为的细观损伤破坏机理。研究结果表明:当煤体进入屈服阶段后,微裂隙结构彼此相互贯通并形成随意的漫射分布,声发射(AE)定位信号表现出明显的激增现象,这一现象可以作为煤体失稳破坏前的预警信息;围压的作用改变了煤体在宏观尺度下的纵向劈裂破坏模式,导致次生裂纹数量增加,并形成多个共轭剪切面,使煤体由纵向劈裂模式和剪切破裂模式向“Y”形剪切破坏模式和多剪切破坏模式转变;煤体宏观主破裂面与轴向应力方向形成的破裂夹角随围压变化呈正相关递增关系。在应力-应变全过程不同阶段中,煤体轴向应力与轴向应变对应微裂纹扩展演化的敏感性阈值指标,可为煤体宏细观损伤破坏机理研究提供借鉴。 展开更多
关键词 煤体 声发射 离散元 宏细观 损伤破坏
在线阅读 下载PDF
A micromechanical damage model for rocks and concretes under triaxial compression
19
作者 任中俊 彭向和 +2 位作者 胡宁 杨春和 Xing-ming GUO 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2009年第3期323-333,共11页
Based on analysis of deformation in an infinite isotropic elastic matrix containing an embedded elliptic crack, subject to far field triaxial compressive stress, the energy release rate and a mixed fracture criterion ... Based on analysis of deformation in an infinite isotropic elastic matrix containing an embedded elliptic crack, subject to far field triaxial compressive stress, the energy release rate and a mixed fracture criterion are obtained by using an energy balance approach. The additional compliance tensor induced by a single closed elliptic microcrack in a representative volume element and its in-plane growth is derived. The additional compliance tensor induced by the kinked growth of the elliptic microcrack is also obtained. The effect of the microcracks, randomly distributed both in geometric characteristics and orientations, is analyzed with the Taylor's scheme by introducing an appropriate probability density function. A micromechanical damage model for rocks and concretes under triaxial compression is obtained and experimentally verified. 展开更多
关键词 elliptic microcrack in-plane growth kinked growth energy release rate micro-macro damage model
在线阅读 下载PDF
人工智能法律应用的发展瓶颈及方法论应对 被引量:5
20
作者 王燕玲 《政法论丛》 北大核心 2025年第2期141-155,共15页
人工智能法律应用是法治现代化的重要一环,其发展面临准确性、效率性、安全性和道德性等问题。对于这些问题,需要从宏观和微观两个层面的方法论加以应对。在宏观层面,应遵从体系性原理。一方面,在法治生态系统的视角下构建人工智能法律... 人工智能法律应用是法治现代化的重要一环,其发展面临准确性、效率性、安全性和道德性等问题。对于这些问题,需要从宏观和微观两个层面的方法论加以应对。在宏观层面,应遵从体系性原理。一方面,在法治生态系统的视角下构建人工智能法律应用系统,避免人工智能法律应用的研发违反法律和道德。另一方面,应重视系统的生长性,在科学的底层系统和底层逻辑的基础上构建人工智能法律精准应用,保证人工智能法律应用的可靠性和动态性;在微观层面,应遵从协同性原理,以算法透明、规则科学以及应用可靠为基本路径,将机器的逻辑思维优势、人类的形象思维与创造思维优势有机结合。 展开更多
关键词 人工智能法律应用困境 法律与技术的融合 宏观方法论 微观方法论
在线阅读 下载PDF
上一页 1 2 77 下一页 到第
使用帮助 返回顶部