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Effects of Different Tillage Systems on Soil Properties,Root Growth,Grain Yield,and Water Use Efficiency of Winter Wheat (Triticum aestivum L.) in Arid Northwest China 被引量:33
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作者 HUANG Gao-bao CHAI Qiang +1 位作者 FENG Fu-xue YU Ai-zhong 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2012年第8期1286-1296,共11页
Studies on root development, soil physical properties, grain yield, and water-use efficiency are important for identifying suitable soil management practices for sustainable crop production. A field experiment was con... Studies on root development, soil physical properties, grain yield, and water-use efficiency are important for identifying suitable soil management practices for sustainable crop production. A field experiment was conducted from 2006 through 2008 in arid northwestern China to determine the effects of four tillage systems on soil properties, root development, water-use efficiency, and grain yield of winter wheat (Triticum aestivum L.). The cultivar Fan 13 was grown under four tillage systems:conventional tillage (CT) without wheat stubble, no-tillage without wheat stubble mulching (NT), no-tillage with wheat stubble standing (NTSS), and no-tillage with wheat stubble mulching (NTS). The soil bulk density (BD) under CT system increased gradually from sowing to harvest, but that in NT, NTSS, and NTS systems had little change. Compared to the CT system, the NTSS and NTS systems improved total soil water storage (0-150 cm) by 6.1-9.6 and 10.5- 15.3% before sowing, and by 2.2-8.9 and 13.0-15.1% after harvest, respectively. The NTSS and NTS systems also increased mean dry root weight density (DRWD) as compared to CT system. The NTS system significantly improved water-use efficiency by 17.2-17.5% and crop yield by 15.6-16.8%, and the NTSS system improved that by 7.8-9.6 and 7.0-12.8%, respectively, compared with the CT system. Our results suggested that Chinese farmers should consider adopting conservation tillage practices in arid northwestern China because of benefits to soil bulk density, water storage, root system, and winter wheat yield. 展开更多
关键词 conservation tillage soil water storage bulk density water use efficiency winter wheat (Triticum aestivumL.) root system grain yield
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改善造纸法烟草基片松厚度的研究 被引量:33
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作者 温洋兵 罗冲 +3 位作者 胡惠仁 王亮 孙德平 姚元军 《中国造纸》 CAS 北大核心 2012年第4期30-33,共4页
研究了造纸法烟草基片生产过程中,烟梗浆与烟末浆比例、木浆和沉淀碳酸钙(PCC)用量对烟草基片松厚度和抗张强度的影响。结果表明,适宜的木浆添加比例约为20%;增加烟草浆中烟末浆的比例对基片的松厚度有利,但是对烟草基片的强度性能具有... 研究了造纸法烟草基片生产过程中,烟梗浆与烟末浆比例、木浆和沉淀碳酸钙(PCC)用量对烟草基片松厚度和抗张强度的影响。结果表明,适宜的木浆添加比例约为20%;增加烟草浆中烟末浆的比例对基片的松厚度有利,但是对烟草基片的强度性能具有负面影响,烟草浆中适宜的烟末浆比例约为50%。 展开更多
关键词 烟草基片 松厚度 木浆 烟梗浆 烟末浆 PCC
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Bulk transfer coefficients of the atmospheric momentum and sensible heat over desert and Gobi in arid climate region of Northwest China 被引量:22
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作者 张强 卫国安 +1 位作者 黄荣辉 曹晓彦 《Science China Earth Sciences》 SCIE EI CAS 2002年第5期468-480,共13页
By utilizing the data of the intensive observation period (May-June, 2000) of Dunhuang land-surface process field experiment that belongs to 'Land-atmosphere Interactive Field Experiment over Arid Region of Northw... By utilizing the data of the intensive observation period (May-June, 2000) of Dunhuang land-surface process field experiment that belongs to 'Land-atmosphere Interactive Field Experiment over Arid Region of Northwest China', the bulk momentum transfer coefficient Cd and bulk sensible heat transfer coefficient Ch between surface and atmosphere over desert and Gobi in the arid region are determined according to three different methods. The result shows that, though these bulk transfer coefficients are different, they are in the same order. Especially, the means of Cd and Ch are close. Moreover, through analyzing the wind direction, the interference of the building near the observational station with the data is eliminated. From this, the relation between the bulk transfer coefficients and the bulk Richardson number and the range of the typical values of the bulk transfer coefficients over desert and Gobi in the typical arid region are obtained. 展开更多
关键词 DESERT and Gobi bulk transfer coefficient bulk RICHARDSON number interference of building.
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连年深松和施用有机肥对土壤肥力及玉米产量的影响 被引量:23
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作者 宫亮 安景文 +2 位作者 邢月华 刘艳 孙文涛 《土壤》 CAS CSCD 北大核心 2016年第6期1092-1099,共8页
通过8年的田间定位试验,研究了不同耕作方法及有机肥用量对春玉米产量和土壤理化性状的影响。结果表明,连年深松能显著降低10~20 cm和20~30 cm土壤体积质量,施用有机肥30 000 kg/hm^2以上能显著降低10~20 cm土壤体积质量;深松导致耕层... 通过8年的田间定位试验,研究了不同耕作方法及有机肥用量对春玉米产量和土壤理化性状的影响。结果表明,连年深松能显著降低10~20 cm和20~30 cm土壤体积质量,施用有机肥30 000 kg/hm^2以上能显著降低10~20 cm土壤体积质量;深松导致耕层土壤有机质、全氮和全磷含量呈下降趋势,碱解氮和速效磷略有增加;耕层土壤有机质、全氮、碱解氮和速效磷含量随有机肥用量的增加而显著增加,全磷、全钾和速效钾含量增加幅度与有机肥用量无关;深松和施用有机肥均能显著增加玉米产量,施用有机肥的增产效果好于深松,但其增产速率随有机肥用量增加而降低。连年深松对改善土壤理化性质和提高玉米产量的效果好于隔年深松,且在施用有机肥的条件下效果更好。 展开更多
关键词 耕作 体积质量 有机肥 玉米
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孔隙流体地震特性的计算 被引量:20
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作者 云美厚 易维启 《石油物探》 EI CSCD 2001年第2期13-20,28,共9页
孔隙流体对岩石地震特性的影响为采油地震监测的物理基础 ,搞清地层条件下孔隙流体地震特性的变化规律对提高地震监测的精度具有重要的意义。在收集、分析前人研究结果的基础上 ,本文导出了当地层压力从高于饱和压力降低到低于饱和压力... 孔隙流体对岩石地震特性的影响为采油地震监测的物理基础 ,搞清地层条件下孔隙流体地震特性的变化规律对提高地震监测的精度具有重要的意义。在收集、分析前人研究结果的基础上 ,本文导出了当地层压力从高于饱和压力降低到低于饱和压力时 ,从原油中所脱出的游离气的体积百分含量计算式 ,并计算和分析了不同温度压力下原油、油气混合物以及地层水的地震特性 。 展开更多
关键词 孔隙流体 地震特性 原油 采油地震监测 地层水 密度 速度 体积 模量 温度 压力
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TiZr-base Bulk Metallic Glass with over 50 mm in Diameter 被引量:21
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作者 M. Q. Tang H.F. Zhang Z. W. Zhu H.M. Fu A.M. Wang H. Li Z.Q. Hu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2010年第6期481-486,共6页
Low-cost TiZr-base bulk metallic glasses (BMGs) (Ti36.1Zr33.2Ni5.8Be24.9)100-xCux (x=5, 7 and g) with a maximum size of over 50 mm in diameter were developed by optimizing the alloy composition. The idea is init... Low-cost TiZr-base bulk metallic glasses (BMGs) (Ti36.1Zr33.2Ni5.8Be24.9)100-xCux (x=5, 7 and g) with a maximum size of over 50 mm in diameter were developed by optimizing the alloy composition. The idea is initiated by selecting a particular microstructure comprising primary β-Ti dendrite and amorphous phase. Afterwards, based on this composition of amorphous phase, a class of TiZr-base bulk metallic glasses was designed step by step to reach the optimum composition range. The glass transition temperature (Tg), initial crystallization temperature (Tx) and width of supercooled region (AT) of (mi36.iZr33.2Nis.8Be24.9)91Cu9 BMG are 611, 055 and 44 K, respectively. The (Ti36.1Zr33.2Ni5.8Be24.9)91Cu9 BMG exhibits low density of 5.541 g·cm-3 and high compressive fracture strength of 1800 MPa, which promises the potential application as structural materials. 展开更多
关键词 TiZr-base alloy bulk metallic glass (BMG) Fracture strength
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DEM parameter calibration of cohesive bulk materials using a simple angle of repose test 被引量:22
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作者 Thomas Roessler Andre Katterfeld 《Particuology》 SCIE EI CAS CSCD 2019年第4期105-115,共11页
The numerical effort of discrete element method (DEM) simulations results in a general idealisation of DEM models that makes the calibration crucial to obtaining realistic simulation results. The angle of repose test ... The numerical effort of discrete element method (DEM) simulations results in a general idealisation of DEM models that makes the calibration crucial to obtaining realistic simulation results. The angle of repose test has become a standard test for the calibration of DEM parameters of cohesionless bulk materials and is extensively discussed in the literature. One of the most used test methods is the pull-up test of a hollow cylinder filled with bulk material. This paper presents how this basic pull-up test can also be used for the calibration of DEM parameters of cohesive materials by changing the analysis criteria. In contrast to analysing the static angle of repose, the focus lies on the macroscopic flow behaviour during the lifting of the cylinder. Reproducible phases of flow are identified in experiments: the build-up of a stable bulk material column, the convex bending of the column, and the beginning of collapse of the column. Furthermore, the phases are independent of the size and lifting velocity. The convex bending of the bulk-material column combined with the moment of first collapse are introduced as new measurable calibration criteria. These experimental results of wet sand are used for the calibration of related DEM parameters using a simplified JKR cohesion model. The DEM calibration including an analysis algorithm that fits the experimental flow behaviour and the final selection of the relevant parameters (i.e., sliding friction coefficient, rolling friction coefficient, and cohesion energy density) is presented in detail. 展开更多
关键词 DISCRETE ELEMENT method ANGLE of repose COHESIVE bulk material Calibration
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Study of Soil-Water Characteristic Curve Using Microscopic Spherical Particle Model 被引量:22
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作者 YANG Song LU Ting-Hao 《Pedosphere》 SCIE CAS CSCD 2012年第1期103-111,共9页
When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided i... When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model. 展开更多
关键词 connecting liquid bridge contact angle hysteresis dry bulk density physical model
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鸭蛋大小等级模型研究 被引量:18
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作者 王巧华 余佑生 +3 位作者 宗望远 陈小伟 刘剑英 文友先 《华中农业大学学报》 CAS CSCD 北大核心 2001年第6期578-583,共6页
应用机器视觉 ,研究出鸭蛋大小自动分级模型。鸭蛋的面积尺寸是鸭蛋大小分级的重要依据 ,鸭蛋的重量与所成像的像素面积成正比。鸭蛋大小等级模型具有显著性和可靠性 ,鸭蛋大小的检测误差在± 3g之间 。
关键词 鸭蛋大小自动分级模型 机器视觉技术 鸭蛋品质
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完全电视胸腔镜手术诊治113例原发性纵隔肿瘤的临床分析 被引量:20
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作者 房渝 黄春 +2 位作者 李军 刘恒 秦治明 《第三军医大学学报》 CAS CSCD 北大核心 2016年第18期2087-2090,共4页
目的 探讨完全电视胸腔镜手术(video-assisted thoracoscopic surgery,VATS)在切除纵隔肿瘤,尤其是大体积和侵袭性纵隔肿瘤中的临床价值。方法 回顾性分析了我科2011年1月至2014年12月经VATS行纵隔肿瘤切除手术患者113例,男性51例,女... 目的 探讨完全电视胸腔镜手术(video-assisted thoracoscopic surgery,VATS)在切除纵隔肿瘤,尤其是大体积和侵袭性纵隔肿瘤中的临床价值。方法 回顾性分析了我科2011年1月至2014年12月经VATS行纵隔肿瘤切除手术患者113例,男性51例,女性62例。年龄9~78岁(中位年龄50岁),肿瘤最大径线值1.5~13 cm(中位径线值4 cm)。记录围术期各项观察指标并行统计学分析。结果 113例纵隔肿瘤均在VATS下完成,术中出血量10~800 m L(中位出血量100 m L),术后住院时间2~18 d(中位术后住院时间5 d),手术时间40~330 min(中位手术时间90 min)。统计分析指出直径〉6 cm的纵隔肿瘤共28例(占24.8%),围术期无死亡和相关并发症发生,术后随访未见肿瘤复发。相对于直径〈6 cm的肿瘤,直径〉6 cm的纵隔肿瘤手术时间延长(P〈0.001),术中出血量增加(P〈0.001),但术后住院时间未见明显延长。4例侵袭性纵隔肿瘤(3例恶性胸腺瘤和1例畸胎瘤)行VATS,围术期无死亡病例和并发症发生,术后随访1例复发。结论 VATS广泛应用于纵隔肿瘤的切除,同时大体积以及侵袭性纵隔肿瘤不是VATS的禁忌。在一定条件下,VATS对大体积以及侵袭性纵隔肿瘤的治疗可以达到和传统开放手术相似的治疗效果,同时能够降低手术创伤,减轻术后疼痛,缩短患者住院时间以及减少术后并发症,且安全、有效、经济。 展开更多
关键词 电视胸腔镜手术 纵隔肿瘤 侵袭性 大体积
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Direct Comparative Analyses of 10X Genomics Chromium and Smart-seq2 被引量:19
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作者 Xiliang Wang Yao He +2 位作者 Qiming Zhang Xianwen Ren Zemin Zhang 《Genomics, Proteomics & Bioinformatics》 SCIE CAS CSCD 2021年第2期253-266,共14页
Single-cell RNA sequencing(scRNA-seq)is generally used for profiling transcriptome of individual cells.The droplet-based 10X Genomics Chromium(10X)approach and the plate-based Smart-seq2 full-length method are two fre... Single-cell RNA sequencing(scRNA-seq)is generally used for profiling transcriptome of individual cells.The droplet-based 10X Genomics Chromium(10X)approach and the plate-based Smart-seq2 full-length method are two frequently used scRNA-seq platforms,yet there are only a few thorough and systematic comparisons of their advantages and limitations.Here,by directly comparing the scRNA-seq data generated by these two platforms from the same samples of CD45cells,we systematically evaluated their features using a wide spectrum of analyses.Smart-seq2 detected more genes in a cell,especially low abundance transcripts as well as alternatively spliced transcripts,but captured higher proportion of mitochondrial genes.The composite of Smart-seq2 data also resembled bulk RNA-seq data more.For 10X-based data,we observed higher noise for mRNAs with low expression levels.Approximately 10%30%of all detected transcripts by both platforms were from non-coding genes,with long non-coding RNAs(lncRNAs)accounting for a higher proportion in 10X.10X-based data displayed more severe dropout problem,especially for genes with lower expression levels.However,10X-data can detect rare cell types given its ability to cover a large number of cells.In addition,each platform detected distinct groups of differentially expressed genes between cell clusters,indicating the different characteristics of these technologies.Our study promotes better understanding of these two platforms and offers the basis for an informed choice of these widely used technologies. 展开更多
关键词 Single-cell RNA sequencing 10X Smart-seq2 bulk RNA-seq Comparison
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散货码头计算机动画模拟研究 被引量:4
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作者 彭传圣 《港口装卸》 2001年第1期1-6,共6页
应用计算机模拟技术能够为港口码头规划设计和营运管理提供定量化的决策支持信息。本文在简介由交通部资助开发的通用专业化散货码头计算机动画模拟模型的基础上 ,介绍应用该模型提供的手段为某港煤炭码头建立模拟模型 ,研究该码头营运... 应用计算机模拟技术能够为港口码头规划设计和营运管理提供定量化的决策支持信息。本文在简介由交通部资助开发的通用专业化散货码头计算机动画模拟模型的基础上 ,介绍应用该模型提供的手段为某港煤炭码头建立模拟模型 ,研究该码头营运条件与码头通过能力的关系的情况。 展开更多
关键词 计算机模拟 动画 码头规划 营运 散货码头 模型 开发 建模
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Effects of Cu,Fe and Co addition on the glass-forming ability and mechanical properties of Zr-Al-Ni bulk metallic glasses 被引量:19
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作者 LI YanHui ZHANG Wei +1 位作者 DONG Chuang AKIHIRO Makino 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第12期2367-2371,共5页
The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly e... The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy.Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm.However,addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA.In addition,the plasticity of the BMG can be improved by adding of Cu,while the strength is decreased slightly.Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa.Addition of Co brings an increase of strength but a lower of plasticity,and additional Fe reduces the strength and plasticity simultaneously. 展开更多
关键词 bulk metallic glasses glass-forming ability mechanical properties Zr-Al-Ni alloys
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Spatial Variability of Soil Organic Carbon Under Maize Monoculture in the Song-Nen Plain, Northeast China 被引量:19
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作者 WANG Zong-Ming , ZHANG Bai, SONG Kai-Shan, LIU Dian-Wei and REN Chun-Ying Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Sciences, Changchun 130012 (China) 《Pedosphere》 SCIE CAS CSCD 2010年第1期80-89,共10页
Soil organic carbon (SOC) and its relationship with landscape attributes are important for evaluating current regional, continental, and global carbon stores. Data of SOC in surface soils (0–20 cm) of four main soils... Soil organic carbon (SOC) and its relationship with landscape attributes are important for evaluating current regional, continental, and global carbon stores. Data of SOC in surface soils (0–20 cm) of four main soils, Cambisol, Arenosol, Phaeozem, and Chernozem, were collected at 451 locations in Nongan County under maize monoculture in the Song-Nen Plain, Northeast China. The spatial characteristics of soil organic carbon were studied, using geographic information systems (GIS) and geostatistics. Effects of other soil physical and chemical properties, elevation, slope, and soil type on SOC were explored. SOC concentrations followed a normal distribution, with an arithmetic mean of 14.91 g kg-1 . The experimental variogram of SOC was fitted with a spherical model. There were significant correlations between soil organic carbon and bulk density (r =-0.374**), pH (r = 0.549**), total nitrogen (r = 0.781**), extractable phosphorus (r =-0.109*), exchangeable potassium (r = 0.565**), and cation exchange capacity (r = 0.313**). Generally, lower SOC concentrations were significantly associated with high elevation (r =-0.429**). Soil organic carbon was significantly negatively correlated with slope gradient (r =-0.195**). Samples of the Cambisol statistically had the highest SOC concentrations, and samples of the Arenosol had the lowest SOC value. 展开更多
关键词 GEOSTATISTICS slope soil bulk density spatial distribution
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细小纤维对造纸法烟草薄片基片物理性能的影响 被引量:18
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作者 王亮 罗冲 +3 位作者 温洋兵 唐向兵 李旺 胡惠仁 《中国造纸》 CAS 北大核心 2013年第9期35-39,共5页
利用漂白硫酸盐针叶木浆制备不同长度的细小纤维,考察其对烟草薄片基片物理性能(抗张强度、松厚度、柔软性能、粗糙度和透气度)和浆料滤水性能的影响,并对细小纤维用量进行优化。实验结果表明,随着细小纤维平均长度的降低,基片的抗张强... 利用漂白硫酸盐针叶木浆制备不同长度的细小纤维,考察其对烟草薄片基片物理性能(抗张强度、松厚度、柔软性能、粗糙度和透气度)和浆料滤水性能的影响,并对细小纤维用量进行优化。实验结果表明,随着细小纤维平均长度的降低,基片的抗张强度提高,与此同时松厚度和柔软性能受到影响,浆料的滤水性能下降;木浆纤维用量15%、添加平均长度0.622 mm的细小纤维可较好地改善基片的各项物理性能,其中细小纤维合适的用量为1.5%;与传统工艺(木浆纤维用量20%)相比,木浆纤维用量降低了25%左右,减少了卷烟木质杂气的产生量。 展开更多
关键词 造纸法烟草薄片 基片 细小纤维 抗张强度 松厚度 柔软性
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Eddy covariance measurements of water vapor and CO_2 fluxes above the Erhai Lake 被引量:18
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作者 LIU HuiZhi FENG JianWu +2 位作者 SUN JiHua WANG Lei XU AnLun 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第3期317-328,共12页
Measurement of turbulence fluxes were performed over the Erhai Lake using eddy covariance(EC) method.Basic physical parameters in the lake-air interaction processes,such as surface albedo of the lake,aerodynamic rough... Measurement of turbulence fluxes were performed over the Erhai Lake using eddy covariance(EC) method.Basic physical parameters in the lake-air interaction processes,such as surface albedo of the lake,aerodynamic roughness length,bulk transfer coefficients,etc.,were investigated using the EC data in 2012.The characteristics of turbulence fluxes over the lake including momentum flux,sensible heat flux,latent heat flux,and CO2 flux,and their controlling factors were analyzed.The total annual evaporation of the lake was also estimated based on the artificial neural network(ANN) gap-filling technique.Results showed that the total annual evaporation in 2012 was 1165 ± 15 mm,which was larger than the annual precipitation(818 mm).Local circulation between the lake and the surrounding land was found to be significant throughout the year due to the land-lake breeze or the mountain-valley breeze in this area.The prevailing winds of southeasterly and northwesterly were observed throughout the year.The sensible heat flux over this plateau lake usually had a few tens of W m-2,and generally became negative in the afternoon,indicating that heat was transferred from the lake to the atmosphere.The sensible heat flux was governed by the lake-air temperature difference and had its maximum in the early morning.The diurnal variation of the latent heat flux was controlled by vapor pressure deficit with a peak in the afternoon.The latent heat flux was dominant in the partition of available energy in daytime over this lake.The lake acted as a weak CO2 source to the atmosphere except for the midday of summer.Seasonal variations of surface albedo over the lake were related to the solar elevation angle and opacity of the water.Furthermore,compared with the observation data,the surface albedo estimated by CLM4-LISSS model was underestimated in winter and overestimated in summer. 展开更多
关键词 Erhai Lake eddy covariance method surface roughness length bulk transfer coefficients
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Bulk Flow方法分析孔型密封转子动力特性的有效性 被引量:14
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作者 晏鑫 李军 丰镇平 《西安交通大学学报》 EI CAS CSCD 北大核心 2009年第1期24-28,共5页
基于Kleynhans和Childs的两控制容积等温BF(Bulk Flow)模型,通过增加能量方程和理想气体状态方程,建立了理想气体BF方法的数学模型,来预测和分析孔型密封转子在偏心状态下的静力学和动力学特性.由于转子在密封中心附近做微小涡动,故可... 基于Kleynhans和Childs的两控制容积等温BF(Bulk Flow)模型,通过增加能量方程和理想气体状态方程,建立了理想气体BF方法的数学模型,来预测和分析孔型密封转子在偏心状态下的静力学和动力学特性.由于转子在密封中心附近做微小涡动,故可通过采用摄动方法使得NS方程的求解过程得到较大的简化,再通过迭代求解简化后的零阶和一阶摄动方程组,就可以求出孔型密封的流场和动力特性系数.以此为依据发展了相关程序,计算出了不同工况条件下孔型密封的转子动力特性系数与激振频率的关系,通过与已有的实验数据和等温BF模型的计算结果进行对比,验证了理想气体BF模型及相关求解方法的有效性.结果表明:理想气体BF模型的预测结果与实验数据吻合良好,且优于等温BF模型的计算结果,证明了该理想气体BF模型的正确性和计算方法的可靠性.该方法可用于孔型密封动力特性的预测. 展开更多
关键词 孔型密封 bulk Flow方法 两控制容积 转子动力学特性
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非晶态合金制备方法 被引量:9
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作者 贾彬彬 张文丛 +1 位作者 夏龙 王卫卫 《轻合金加工技术》 CAS 北大核心 2006年第10期20-24,共5页
对现有的制备非晶的各种方法进行了综述,重点介绍了大块非晶的制备方法,介绍并分析了大块非晶合金成分的选择原则,对非晶制备方法进行了明确的分类,并对它们的优缺点进行了讨论和初步的对比。提出了非晶制备领域存在的问题及发展方向。
关键词 非晶合金 大块 制备
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A general synthetic strategy to monolayer graphene 被引量:14
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作者 Youqi Zhu Tai Cao +3 位作者 Chuanbao Cao Xilan Ma Xingyan Xu Yadong Li 《Nano Research》 SCIE EI CAS CSCD 2018年第6期3088-3095,共8页
The emergence and establishment of new techniques for material fabrication are of fundamental importance in the development of materials science. Thus, we herein report a general synthetic strategy for the preparation... The emergence and establishment of new techniques for material fabrication are of fundamental importance in the development of materials science. Thus, we herein report a general synthetic strategy for the preparation of monolayer graphene. This novel synthetic method is based on the direct solid-state pyrolytic conversion of a sodium carboxylate, such as sodium gluconate or sodium citrate, into monolayer graphene in the presence of Na2CO3. In addition, gram-scale quantities of the graphene product can be readily prepared in several minutes. Analysis using Raman spectroscopy and atomic force microscopy clearly demonstrates that the pyrolytic graphene is composed of a monolayer with an average thickness of - 0.50 nm. Thus, the present pyrolytic conversion can overcome the issue of the low monolayer contents (i.e., 1 wt.%-12 wt.%) obtained using exfoliation methods in addition to the low yields of chemical vapor deposition methods. We expect that this novel technique may be suitable for application in the preparation of monolayer graphene materials for batteries, supercapacitors, catalysts, and sensors. 展开更多
关键词 monolayer graphene pyrolytic conversion sodium carboxylate bulk production
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The bulk transfer coefficients and surface fluxes on the western Tibetan Plateau 被引量:13
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作者 Guoping Li Tingyang Duan Yuanfa Gong 《Chinese Science Bulletin》 SCIE EI CAS 2000年第13期1221-1226,共6页
On the gradient observational data of the atmospheric surface layer from September 1997 to December 1998 collected by two sets of Automatic Weather Station (AWS) installed in Gaize and Shiquanhe on the western Tibetan... On the gradient observational data of the atmospheric surface layer from September 1997 to December 1998 collected by two sets of Automatic Weather Station (AWS) installed in Gaize and Shiquanhe on the western Tibetan Plateau, mean surface roughness lengths at the two stations above are determined to be 2.7 and 2.9 cm, respectively. The bulk transfer coefficients each day are computed by the profile-flux method, means of the bulk transfer coefficient for momentum (i.e. drag coefficient) in 1998 are 4.83×10-3 and 4.75×103 at the two stations. The surface fluxes of momentum, sensible heat and latent heat each day are further estimated by the bulk formulas, annual mean of these fluxes is 3.4×10-2 and 1.8×102N/m2, 73.1 and 67.2 W/m2, 15.4 and 2.9 W/m2, respectively. The diurnal and seasonal variations are obtained by a composite method and the relationships among the heat transfers between land and atmosphere, plateau monsoon and plateau rain season are also discussed. 展开更多
关键词 WESTERN TIBETAN PLATEAU AWS data SURFACE ROUGHNESS length bulk transfer coefficient SURFACE flux.
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