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Enhanced Roles of Carbon Architectures in High?Performance Lithium?Ion Batteries
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作者 Lu Wang Junwei Han +2 位作者 Debin Kong Ying Tao Quan-Hong Yang 《纳微快报:英文版》 CAS CSCD 2019年第1期78-100,共23页
Lithium-ion batteries(LIBs),which are high-energydensity and low-safety-risk secondary batteries,are underpinned to the rise in electrochemical energy storage devices that satisfy the urgent demands of the global ener... Lithium-ion batteries(LIBs),which are high-energydensity and low-safety-risk secondary batteries,are underpinned to the rise in electrochemical energy storage devices that satisfy the urgent demands of the global energy storage market.With the aim of achieving high energy density and fast-charging performance,the exploitation of simple and low-cost approaches for the production of high capacity,high density,high mass loading,and kinetically ion-accessible electrodes that maximize charge storage and transport in LIBs,is a critical need.Toward the construction of high-performance electrodes,carbons are promisingly used in the enhanced roles of active materials,electrochemical reaction frameworks for high-capacity noncarbons,and lightweight current collectors.Here,we review recent advances in the carbon engineering of electrodes for excellent electrochemical performance and structural stability,which is enabled by assembled carbon architectures that guarantee sufficient charge delivery and volume fluctuation buffering inside the electrode during cycling.Some specific feasible assembly methods,synergism between structural design components of carbon assemblies,and electrochemical performance enhancement are highlighted.The precise design of carbon cages by the assembly of graphene units is potentially useful for the controlled preparation of high-capacity carbon-caged noncarbon anodes with volumetric capacities over 2100 mAh cm?3.Finally,insights are given on the prospects and challenges for designing carbon architectures for practical LIBs that simultaneously provide high energy densities(both gravimetric and volumetric)and high rate performance. 展开更多
关键词 Lithium?ion BATTERY Carbon architecture Energy DENSITY Power DENSITY Assembly
Fabricating high-performance sodium ion capacitors with P2-Na0.67Co0.5Mn0.5O2 and MOF-derived carbon 预览
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作者 Haichen Gu Lingjun Kong +3 位作者 Huijuan Cui Xianlong Zhou Zhaojun Xie Zhen Zhou 《能源化学:英文版》 SCIE EI CAS CSCD 2019年第1期79-84,共6页
Sodium ion capacitors(SICs)have been considered as a kind of promising devices to achieve both high power and energy density.However,it is still a challenge to achieve high energy output at elevated power delivery due... Sodium ion capacitors(SICs)have been considered as a kind of promising devices to achieve both high power and energy density.However,it is still a challenge to achieve high energy output at elevated power delivery due to the poor rate capability of battery-type electrode materials and the kinetic mismatch with capacitor-type electrode materials.In this work,to fabricate SICs,P2-Na0.67Co0.5Mn0.5O2(P2-NCM)was chosen as the battery-type cathode material,and a typical metal-organic framework(MOF)material,zeolitic imidazolate framework-8(ZIF-8)derived carbon(ZDC)was utilized as the capacitor-type anode material.Due to the kinetic match and high-rate performance of both electrodes,the ZDC//P2-NCM SICs exhibited an energy output of 18.8 Wh kg^-1 at a high power delivery of 12.75 kW kg^-1. 展开更多
关键词 Energy DENSITY Power DENSITY P2-phase material Zeolitic IMIDAZOLATE framework-8 Sodium ion capacitors
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利用小核磁法测定聚乙烯密度 预览
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作者 柳盛 郭凡 +3 位作者 王会能 王学智 刘鹏 刘文才 《合成树脂及塑料》 CAS 北大核心 2019年第2期62-66,共5页
考察了小核磁法测定聚乙烯密度的重复性及准确性,并分别采用小核磁法与密度梯度柱法测试了高密度聚乙烯、低密度聚乙烯和线型低密度聚乙烯的密度。结果表明,采用小核磁法与密度梯度柱法测定聚乙烯密度值之差为:线型低密度聚乙烯粒料≤0.... 考察了小核磁法测定聚乙烯密度的重复性及准确性,并分别采用小核磁法与密度梯度柱法测试了高密度聚乙烯、低密度聚乙烯和线型低密度聚乙烯的密度。结果表明,采用小核磁法与密度梯度柱法测定聚乙烯密度值之差为:线型低密度聚乙烯粒料≤0.0001g/cm^3,线型低密度聚乙烯粉料≤0.0002g/cm^3;低密度聚乙烯粒料≤0.0001g/cm^3,低密度聚乙烯粉料≤0.0002g/cm^3,高密度聚乙烯粒料≤0.0001g/cm^3,高密度聚乙烯粉料≤0.0004g/cm^3。确定小核磁法测定聚乙烯密度满足密度梯度柱法要求的精密度及准确度,两种方法可以互相替换。小核磁法测定聚乙烯密度的主要影响因素有试样含水、沾油或混入其他杂质,试样预热时间不足30min或磁体衰减,同时提出了相应的解决措施。 展开更多
关键词 聚乙烯 密度 小核磁法 密度梯度柱法 粒料 粉料
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终碾温度对沥青混凝土压实性的影响研究
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作者 杨乐天 何建新 开鑫 《粉煤灰综合利用》 CAS 2019年第1期10-12,27共4页
为了研究不同终碾温度对沥青混凝土压实性能的影响,本文以90℃~160℃区间为例,通过网篮法以及马歇尔试验研究,分析不同终碾温度下沥青混凝土试件的密度、孔隙率、稳定度和流值的影响情况。结果表明:随着终碾温度的降低,沥青混凝土的孔... 为了研究不同终碾温度对沥青混凝土压实性能的影响,本文以90℃~160℃区间为例,通过网篮法以及马歇尔试验研究,分析不同终碾温度下沥青混凝土试件的密度、孔隙率、稳定度和流值的影响情况。结果表明:随着终碾温度的降低,沥青混凝土的孔隙率增加明显,马歇尔试件稳定度下降,流值增大;终碾温度在100℃时,沥青混凝土的孔隙率可满足小于2%的要求;在正反各70次击实次数时,仅90℃的沥青混合料能满足低于2%孔隙率的要求。研究成果可为冬季沥青混凝土心墙坝加快施工速度、延长施工周期、控制施工质量提供理论依据和技术支持。 展开更多
关键词 沥青混凝土 网篮法 密度 孔隙率
Onshore-offshore wind energy resource evaluation based on synergetic use of multiple satellite data and meteorological stations in Jiangsu Province,China
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作者 Xianglin WEI Yuewei DUAN +2 位作者 Yongxue LIU Song JIN Chao SUN 《地球科学前沿:英文版》 SCIE CAS CSCD 2019年第1期132-150,共19页
The demand for efficient and cost-effective renewable energy is increasing as traditional sources of energy such as oil,coal,and natural gas,can no longer satisfy growing global energy demands.Among renewable energies... The demand for efficient and cost-effective renewable energy is increasing as traditional sources of energy such as oil,coal,and natural gas,can no longer satisfy growing global energy demands.Among renewable energies,wind energy is the most prominent due to its low, manageable impacts on the local environment.Based on meteorological data from 2006 to 2014 and multi-source satellite data (i.e.,Advanced Scatterometer,Quick Scatterometer,and Windsat)from 1999 to 2015,an assessment of the onshore and offshore wind energy potential in Jiangsu Province was performed by calculating the average wind speed,average wind direction,wind power density, and annual energy production (AEP).Results show that Jiangsu has abundant wind energy resources,which increase from inland to coastal areas.In-onshore areas, wind power density is predominantly less than 200 W/m^2, while in offshore areas,wind power density is concentrates in the range of 328-500 W/m^2.Onshore areas comprise more than 13,573.24 km^2,mainly located in eastern coastal regions with good wind farm potential The total wind power capacity in onshore areas could be as much as 2.06×10^5 GWh.Meanwhile,offshore wind power generation in Jiangsu Province is calculated to reach 2×10^6 GWh, which is approximately four times the electricity demand of the entire Jiangsu Province.This study validates the effective application of Advanced Scatterometer,Quick Scatterometer,and Windsat data to coastal wind energy monitoring in Jiangsu.Moreover,the methodology used in this study can be effectively applied to other similar coastal zones. 展开更多
关键词 WIND ENERGY RESOURCE WIND power DENSITY ASCAT QUIKSCAT Windsat
Experimental determination of distributions of soot particle diameter and number density by emission and scattering techniques
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作者 柳华蔚 郑树 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期400-405,共6页
A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C camer... A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C cameras were utilized for the scattering measurement, with consideration of the attenuation effect in the flames according to corresponding absorption coefficients. Distributions of soot particle diameter and number density were simultaneously determined using the measured scattering coefficients and absorption coefficients under multiple wavelengths already measured with a SOC701 V hyper-spectral imaging device, according to the Mie scattering theory. A flame was produced using an axisymmetric laminar diffusion flame burner with 194 mL/min ethylene and 284 L/min air, and distributions of particle diameter and number density for the flame were presented. Consequently, the distributions of soot volume fraction were calculated using these two parameters as well, which were in good agreement with the results calculated according to the Rayleigh approximation,demonstrating that the proposed diagnostic method is capable of simultaneous determination of the distributions of soot particle diameter and number density. 展开更多
关键词 SOOT PARTICLE DIAMETER SOOT PARTICLE NUMBER density SOOT volume FRACTION SCATTERING measurement
玉米新品种鑫瑞36耐密性研究 预览
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作者 赵红克 赵清纯 《作物研究》 2019年第2期114-116,共3页
调查了玉米新品种鑫瑞36在不同种植密度下的农艺性状及产量与产量要素,结果表明,在其他条件一致的情况下,鑫瑞36在种植密度为75000株/hm^2左右时,其产量水平表现最高。
关键词 玉米 栽培 密度 鑫瑞36
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核电主泵铸造泵壳的国产化研制 预览
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作者 王平 唐贤其 +2 位作者 李莉 段红玲 陈冲 《大型铸锻件》 2019年第2期10-12,15共4页
结合计算机凝固过程仿真模拟技术,对核电主泵铸造泵壳的关键铸造技术进行研究,解决了奥氏体-铁素体不锈钢核电铸造泵壳需整体RT检测的问题,并通过确定合适的材料配比和热处理工艺参数,保证铸造泵壳所需的理化性能及金相组织构成,完成了... 结合计算机凝固过程仿真模拟技术,对核电主泵铸造泵壳的关键铸造技术进行研究,解决了奥氏体-铁素体不锈钢核电铸造泵壳需整体RT检测的问题,并通过确定合适的材料配比和热处理工艺参数,保证铸造泵壳所需的理化性能及金相组织构成,完成了首台核电主泵铸造泵壳的国产化研制。 展开更多
关键词 铸造泵壳 致密性 成分和组织控制
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中低温煤焦油窄馏分密度和黏度随温度的变化规律
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作者 胡发亭 朱肖曼 +1 位作者 李军芳 吴艳 《煤炭技术》 CAS 2019年第4期142-144,共3页
以中低温煤焦油为原料,经实沸点蒸馏切割成17个窄馏分,对每个馏分测定其在不同温度下的密度,得出密度随温度的升高而变小,具有很好的线性关系,经过理论计算和推导,得出体胀系数E和线性系数也呈线性关系。依据每个馏分段在不同温度下的... 以中低温煤焦油为原料,经实沸点蒸馏切割成17个窄馏分,对每个馏分测定其在不同温度下的密度,得出密度随温度的升高而变小,具有很好的线性关系,经过理论计算和推导,得出体胀系数E和线性系数也呈线性关系。依据每个馏分段在不同温度下的运动黏度,通过计算得出动力黏度,发现动力黏度随着温度的升高而降低,而且符合Vogel关系式。 展开更多
关键词 中低温煤焦油 实沸点蒸馏 窄馏分 密度 黏度
离子液体[emim]Ac密度和电导率的实验与理论研究 预览
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作者 何丽娟 陈帅帅 +2 位作者 李松波 刘素霞 田宝云 《应用化工》 CAS CSCD 北大核心 2019年第4期798-800,共3页
对离子液体[emim]Ac的密度和电导率进行了实验测定与理论模型关联。结果表明,离子液体[emim]Ac的密度随温度的升高逐渐减小,当温度范围为298.15~338.15 K时,[emim]Ac的密度值变化范围为1 072~ 1 024 kg/m 3;离子液体[emim]Ac的电导率随... 对离子液体[emim]Ac的密度和电导率进行了实验测定与理论模型关联。结果表明,离子液体[emim]Ac的密度随温度的升高逐渐减小,当温度范围为298.15~338.15 K时,[emim]Ac的密度值变化范围为1 072~ 1 024 kg/m 3;离子液体[emim]Ac的电导率随温度的升高逐渐增大,当温度范围为298.15~338.15 K时,[emim]Ac的电导率值变化范围为0.369~0.983 S/m;通过比较离子液体[emim]Ac密度及电导率的理论模型关联数据与实验测定数据,得出[emim]Ac密度及电导率的理论模型关联平均相对偏差和最大相对偏差分别为:0.82%, 2.65%和1.43%,2.91%,关联结果与实验测定结果一致,故认为所选模型可用于实验数据关联。 展开更多
关键词 [emim]Ac 密度 电导率 实验测定 模型关联
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What is the mass of loess in the Loess Plateau of China?
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作者 Yuanjun Zhu Xiaoxu Jia +1 位作者 Jiangbo Qiao Ming’an Shao 《科学通报:英文版》 SCIE EI CSCD 2019年第8期534-539,共6页
The Loess Plateau of China(LP) has the largest and thickest loess deposits in the world. Quantifying the amount of loess in the LP is crucial for investigating the accumulation and erosion of loess, and determining th... The Loess Plateau of China(LP) has the largest and thickest loess deposits in the world. Quantifying the amount of loess in the LP is crucial for investigating the accumulation and erosion of loess, and determining the regional soil and water resource capacity. We used loess thickness data, a pedotransfer function for bulk density(BD), and the clay content data observed in 242 sites across the LP to derive the BD of loess and then estimate the loess mass and its distribution across the LP. The results indicated that the average BD of loess between the surface and bedrock is 1.58 g cm-3, varying from 1.18 to 1.87 g cm-3.The total loess mass is approximately 5.45 ? 1013 t, and the average loess mass over an area of 1 m2 is 169 t, ranging from 1.36 to 585 t. The greatest mass of loess is in the south-central of the LP while the lowest mass of loess is in the northwest and river valley areas. Our estimate of loess mass provides key data for calculating water, carbon, and nutrient storages in the LP, which improves our understanding of soil-water processes and ecohydrological systems in this landscape. 展开更多
关键词 The LOESS PLATEAU LOESS MASS Pedotransfer function Soil EROSION BULK density
Utilization of the superior properties of highly mesoporous PVP modified NiCo2O4 with accessible 3D nanostructure and flower-like morphology towards electrochemical methanol oxidation reaction 预览
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作者 Gracita M.Tomboc Medhen W.Abebe +1 位作者 Anteneh F.Baye Hern Kim 《能源化学:英文版》 SCIE EI CAS CSCD 2019年第2期136-146,共11页
Up to this date,researchers are still facing difficulties to expand the technology of direct methanol fuel cells(DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor perfor... Up to this date,researchers are still facing difficulties to expand the technology of direct methanol fuel cells(DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor performance due to CO poisoning of the leading-high cost anode catalyst.In line with this,we have successfully modified the morphological structure and composition of low cost cobalt based-metal oxides,MCo2O4(M = Zn and Ni),with the simple and noble use of polyvinyl pyrrolidone(PVP) as growth modifier and surface stabilizer during the synthesis of nanoparticles in our previous reports,which shown high electrocatalytic activity and strong stability.Due to the good performance of our PVP modified MCo2O4 towards pseudocapacitor and oxygen evolution reaction applications,we decided to extend our research study to methanol oxidation reaction.Remarkably,PVP modified Ni Co2O4 electrode directly grown on nickel foam substrate via a simple hydrothermal process exhibited better performance compared with PVP modified ZnCo2O4 and NiCo2O4 without PVP.It had obtained a remarkably low onset potential of 0.285 V and high current density of 280 m A cm-2,and shown great stability and high poison tolerance during a continuous CV cycling and Chronoamperometry test,which attained high efficiency of 86.86%and 98.52%,respectively.These positive results of PVP modified Ni Co2O4 electrode towards MOR might be attributed to its hierarchical 3 D nanostructures with highly mesoporous surface and large surface area which may have provided numerous electroactive sites,and the exceptional corrosion stability of Ni Co2O4 electrode in alkaline solution. 展开更多
关键词 NiCo2O4 3D NANOSTRUCTURE ELECTROCHEMICAL METHANOL oxidation Current density
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Protective Effects of Tribulus terrestris,Avena sativa,and White Ginseng Powder on Bone Mineral Density in Hypercholesterolemic Rats 预览
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作者 Mehmet Akdogan Huri Tilla Ilce +1 位作者 Ali Bilgili Basak Hanedan 《药剂与药理学:英文版》 2019年第6期286-292,共7页
This study investigated the effects of the herbal compounds Tribulus terrestris(TT),Avena sativa(AS),white ginseng(WG),and a triple combination(TC)powder on the serum total cholesterol,low-density lipoprotein choleste... This study investigated the effects of the herbal compounds Tribulus terrestris(TT),Avena sativa(AS),white ginseng(WG),and a triple combination(TC)powder on the serum total cholesterol,low-density lipoprotein cholesterol(LDL-C),high-density lipoprotein cholesterol(HDL-C),triglyceride,and the tibial bone mineral density(BMD)levels in rats fed a high-cholesterol diet.This study comprised Group I(normal pellet feed),Group II(pellet feed with 2%cholesterol),Group III(2%cholesterol plus 15%TT),Group IV(2%cholesterol plus 7.5%AS),Group V(2%cholesterol plus 5%WG)and Group VI(2%cholesterol plus 7.5 TT%+3.75%AS,2.5%WG).The serum total cholesterol,LDL-C,HDL-C,triglyceride,and tibial BMD(g/cm2)levels were measured.Significant decrease in the serum HDL-C levels in Group II than Group I,and significant increase in the serum LDL-C levels in Group II than Groups I and VI were determined.The tibial BMD levels were significantly lower in Groups II and IV than Group I.It was determined that WG and TC significantly prevented the serum total cholesterol increase;TC significantly prevented the serum LDL-C increase;and TT,WG,and TC were non-significantly effective in the improvement of tibial BMD levels. 展开更多
关键词 LIPID and LIPOPROTEINS Tribulus terrestris AVENA SATIVA WHITE GINSENG bone mineral density
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播种密度对漯花4087农艺性状及产量的影响 预览
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作者 李飞 李斯佳 +5 位作者 姬小玲 韩昕君 周彦忠 赵月强 高杉 于娜 《作物研究》 2019年第3期191-193,共3页
以漯花4087为材料,设置7个播种密度,研究播种密度对花生农艺性状和产量的影响。结果表明:漯花4087的主茎高和侧枝长随着密度的加大均表现为先增加后降低的趋势;随着密度的增加,漯花4087的单株果数和饱果数不断减少,单株秕果数增加;百果... 以漯花4087为材料,设置7个播种密度,研究播种密度对花生农艺性状和产量的影响。结果表明:漯花4087的主茎高和侧枝长随着密度的加大均表现为先增加后降低的趋势;随着密度的增加,漯花4087的单株果数和饱果数不断减少,单株秕果数增加;百果重、百仁重、出仁率随着密度增加而降低;产量呈现出先增加后降低的趋势。密度为19.5万穴/公顷时漯花4087产量和经济效益最高。 展开更多
关键词 花生 栽培 密度 漯花4087
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Physico-chemical and mechanical properties of Ti3SiC2-based materials elaborated from SiC/Ti by reactive spark plasma sintering
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作者 Faten TURKI Houyem ABDERRAZAK +3 位作者 Frédéric SCHOENSTEIN Florent TêTARD Mohieddine ABDELLAOUI Noureddine JOUINI 《先进陶瓷(英文版)》 CSCD 2019年第1期47-61,共15页
In this paper, the synthesis of Ti3 SiC2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti3 SiC2 is improved u... In this paper, the synthesis of Ti3 SiC2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti3 SiC2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti3 SiC2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic compositions.Detailed analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti3 SiC2. 展开更多
关键词 TI3SIC2 REACTIVE spark plasma sintering(R-SPS) density MECHANICAL properties
Electrically Conductive and Flame Retardant Graphene/Brominated Polystyrene/Maleic Anhydride Grafted High Density Polyethylene Nanocomposites with Satisfactory Mechanical Properties
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作者 Yu Chen Jian Yao +2 位作者 Ming-Ke Xu Zhi-Guo Jiang Hao-Bin Zhang 《高分子科学:英文版》 SCIE CAS CSCD 2019年第5期509-517,共9页
Electrically conductive and flame-retardant maleic anhydride grafted high-density polyethylene(MA-HDPE) nanocomposites with satisfactory mechanical properties are fabricated by melt compounding MA-HDPE with polyethyle... Electrically conductive and flame-retardant maleic anhydride grafted high-density polyethylene(MA-HDPE) nanocomposites with satisfactory mechanical properties are fabricated by melt compounding MA-HDPE with polyethyleneimine(PEI)-modified reduced graphene oxide(PEI@RGO) as the conductive nanofiller and brominated polystyrene(BPS) as the flame retardant. The modification with PEI significantly improves the interfacial compatibility and dispersion of the RGO sheets in the MA-HDPE matrix, leading to electrically conductive nanocomposites with enhanced mechanical properties. Furthermore, the addition of 25 wt% of BPS makes the nanocomposite flame-retardant with a UL-94 V-0 rating. Thus, the multifunctional RGO/MA-HDPE nanocomposites with good electrical, flameretardant, and mechanical properties would have potential applications in construction and pipeline fields. 展开更多
关键词 Polymer NANOCOMPOSITES High density POLYETHYLENE GRAPHENE Electrical CONDUCTIVITY FLAME retardancy
Global Regularity of 2-D Density Patches for Viscous Inhomogeneous Incompressible Flow with General Density:High Regularity Case 预览
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作者 Xian Liao Ping Zhang 《分析理论与应用:英文刊》 CSCD 2019年第2期163-191,共29页
This paper is a continuation work of[26]and studies the propagation of the high-order boundary regularities of the two-dimensional density patch for viscous inhomogeneous incompressible flow.We assume the initial dens... This paper is a continuation work of[26]and studies the propagation of the high-order boundary regularities of the two-dimensional density patch for viscous inhomogeneous incompressible flow.We assume the initial densityρ0=η11Ω0+η21Ω0^c,where(η1,η2)is any pair of positive constants andΩ0 is a bounded,simply connected domain with W^k+2,p(R^2)boundary regularity.We prove that for any positive time t,the density functionρ(t)=η11Ω(t)+η21Ω(t)^c,and the domainΩ(t)preserves the W^k+2,p-boundary regularity. 展开更多
关键词 INHOMOGENEOUS INCOMPRESSIBLE Navier-Stokes equations DENSITY patch striated distributions LITTLEWOOD-PALEY theory
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共词分析法中战略坐标图的改进研究
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作者 李永忠 陈静 谢隆腾 《情报理论与实践》 CSSCI 北大核心 2019年第1期65-69,共5页
[目的/意义]通过研究发现共词分析法中战略坐标图的密度、向心度的不足,提出新的战略坐标图绘制方法,优化了战略坐标图的绘制方法,提高共词分析方法的使用效果。[方法/过程]首先,分析了密度与向心度之间的相关性,指出其不足;其次,基于Pa... [目的/意义]通过研究发现共词分析法中战略坐标图的密度、向心度的不足,提出新的战略坐标图绘制方法,优化了战略坐标图的绘制方法,提高共词分析方法的使用效果。[方法/过程]首先,分析了密度与向心度之间的相关性,指出其不足;其次,基于PageRank和网络密度提出新的战略坐标图绘制方法;最后,以'情报学'为例进行实验对比研究。[结果/结论]通过误差平方和指标和学科主题象限分布差异性,验证了新方法的合理性与科学性。 展开更多
关键词 共词分析 战略坐标图 PAGERANK算法 密度 改进
基于全覆盖粒计算的K-medoids文本聚类算法 预览
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作者 邹雪君 谢珺 +1 位作者 任密蜂 续欣莹 《现代电子技术》 北大核心 2019年第7期162-166,共5页
传统K-medoids聚类算法随机选取初始聚类中心,存在迭代次数增加、聚类结果波动较大的问题,因此提出基于全覆盖粒计算的K-medoids文本聚类算法。该算法定义了全覆盖平均粒度重要性的概念。首先对文本进行Single-Pass粗聚类,利用全覆盖粒... 传统K-medoids聚类算法随机选取初始聚类中心,存在迭代次数增加、聚类结果波动较大的问题,因此提出基于全覆盖粒计算的K-medoids文本聚类算法。该算法定义了全覆盖平均粒度重要性的概念。首先对文本进行Single-Pass粗聚类,利用全覆盖粒度重要性和平均粒度重要性从粗聚类结果中产生初始聚类中心候选集,再基于密度和最大最小距离法则从候选集中选出初始聚类中心。通过实验验证,该算法的聚类迭代次数明显减小,聚类质量明显提高。 展开更多
关键词 文本聚类 K-medoids 全覆盖粒计算 Single-Pass 聚类中心 最大最小距离 密度
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辽宁省蝇类密度监测分析
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作者 王纯玉 丁俊 +3 位作者 张家勇 白玉银 关玉辉 张稷博 《中华卫生杀虫药械》 CAS 2019年第3期254-256,共3页
目的了解辽宁省蝇类的密度、种群构成和季节消长规律,为蝇类防治提供科学依据。方法 2016年4-10月,在辽宁省14个市选择居民区、餐饮外环境、绿化带(公园)、露天农贸市场等4类适合蝇类孳生或活动的场所为监测点,采用诱蝇笼法进行蝇类密... 目的了解辽宁省蝇类的密度、种群构成和季节消长规律,为蝇类防治提供科学依据。方法 2016年4-10月,在辽宁省14个市选择居民区、餐饮外环境、绿化带(公园)、露天农贸市场等4类适合蝇类孳生或活动的场所为监测点,采用诱蝇笼法进行蝇类密度监测。结果 2016年辽宁全省共布笼630个,捕蝇21 640只,蝇类总密度为5.72只/(笼·h),丝光绿蝇、厩腐蝇、家蝇分居前3位,所占比例分别为44.57%、16.77%、13.50%。从环境类型来看,农贸市场的蝇类密度最高,达9.95只/(笼·h);居民区密度最低,为3.35只/(笼·h)。蝇类密度季节消长基本呈单峰曲线,7月达到峰值,密度为11.06只/(笼·h)。结论了解了辽宁省蝇类种群构成及季节消长规律情况,应在蝇类密度高峰期采取综合防治措施,以降低蝇类密度,减少蝇媒传染病的发生。 展开更多
关键词 蝇类 监测 密度 种群构成
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