oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 22 )

2018 ( 490 )

2017 ( 471 )

2016 ( 484 )

Custom range...

Search Results: 1 - 10 of 16018 matches for " 牛琪 "
All listed articles are free for downloading (OA Articles)
Page 1 /16018
Display every page Item
内循环三相流化床反应器内部流场的CFD数值模拟
CFD Simulation of Internal Flow Field of Three-Phase Fluidized Bed Reactor with Internal Circulation
 [PDF]

岑斌, 胡培根,, 凯远, 黄卫星
International Journal of Fluid Dynamics (IJFD) , 2015, DOI: 10.12677/IJFD.2015.32002
Abstract:
应用CFD技术和Euler三相流模型对内循环三相流化床反应器内部流场进行数值模拟,分析讨论了反应器中气含率、固含率及液速的分布及其成因。结果表明反应器中气含率、固含率及液速具有显著不同的特征。相对于降流区,反应器升流区气含率径向分布显著不均匀,但随轴向高度的增加分布不均匀性有所改善,其最大值对称于中心轴线附近,降流区气含率径向分布虽然比较均匀,但气含率远远小于升流区。降流区和升流区固含率径向分布均呈现环核结构特点,即固含率径向分布峰值位于边壁附近,而中心区固含率径向分布相对均匀,且不同轴向高度的径向分布形式接近。升流区液速呈中心大边壁小的特点,但随轴向高度增加径向分布趋于均匀,降流区液速分布呈明显的套管环隙流动特征。
The distribution of gas hold up, solid hold up, liquid velocity in riser and downcomer the reactor was simulated by CFD method. The results showed that: the radial distribution of gas hold up was bigger at the center area and became smoother with the rise of the axial height, while the peak value was in the vicinity of the center axis. The average value of gas hold up increased with in-creasing axial height and became a constant value ultimately. The radial distribution of solid hold up in riser was larger in center and wall area, and had a larger wall region in downcomer also due to the wall effect. The radial distribution of liquid velocity in riser was faster in the center region and smaller on the draft tube wall. But with the increase of the axial height, the difference becomes smaller. The downcomer liquid velocity radial distribution had a typically pipe flow character.
水泥土桩复合地基的抗液化研究
,徐增杰
工程力学 , 2009,
Abstract: 该文通过对未加固与水泥土桩加固模型地基振动台试验,再现了未加固和水泥土桩加固模型土体宏观液化现象,分析了未加固和水泥土桩加固模型土孔隙水压力、孔压比及承压板沉降的变化规律,得出水泥土桩加固液化土地基不仅能够提高地基土的抗液化能力,也能抑制桩间土体的沉降。
公司特征对创业板企业资本结构的影响
贾明,仕良
财会月刊 , 2012,
Abstract: 根据国内外学者的研究,本文将公司特征用盈利能力、企业规模、成长性和资产担保价值这四个指标来衡量,资本结构用负债率来表示。依据深交所公布的年报数据,本文选取了创业板198家上市公司作为研究对象,采用多元线性回归的方法,探究了创业板企业的公司特征对其资本结构的影响。【关键词】盈利能力企业规模成长性资产担保价值资产负债率一、引言资本结构是指企业各种资本的价值构成及其比例。资本结构的合理性在企业运营中起着至关重要的作用。合理安排债权资本比例可以降低企业的综合资本成本率,获得财务杠杆利益,从而增加公司价值。由于我国创业板推出仅两年多,加之其与主板之间在服务对象、准入指标、运行制度和风险特征等方面存在明显差别,故学术界对创业板上市公司资本结构影响因素的研究还比较少,从公司特征角度进行实证研究的更为鲜见。本文拟从公司特征出发,通过实证方法探究其对创业板上市公司资本结构的影响。
Stokes型积分-微分方程Q2-P1元的超收敛分析
SUPERCONVERGENCE ANALYSIS OF Q2-P1 MIXED ELEMENT SOLUTION TO STOKES TYPE INTEGRO-DIFFERENTIAL EQUATIONS

作者,,石东洋
- , 2015,
Abstract: 本文研究Q2-P1混合元对Stokes型积分-微分方程的有限元方法.利用积分恒等式技巧给出了关于流体速度u和压力p的误差估计,特别是在压力p的误差中去掉了影响解的稳定性的因子t-?,改善了以往文献的结果.同时,通过构造适当的插值后处理算子得到了整体超收敛结果.
The Q2-P1 mixed finite element method is discussed for the Stokes type integro-differential equations. The error estimations of fluid velocity u and pressure p are given by the integral identity technique. Especially, in the estimation of pressure p the factor t-? which influences the stability of solution is removed and thus the existing results are improved accordingly. At the same time, the global superconvergence of order is derived based on the interpolation postprocessing approach
地膜机械化技术现状及分析
Current status of and analysis on the mechanical technology of plastic film

温浩军,,纪超
- , 2017,
Abstract: 系统梳理我国地膜机械化技术研究成果,以覆膜播种与残膜回收两大类典型机具为对象,分析对比其结构特征及工作原理,总结剖析当前地膜机械化技术中存在的问题。结果表明:在地膜覆盖机械化技术中,主要存在因苗膜错位、覆土不均、打孔成穴机构不可靠造成的空穴率高、出苗率低等问题。在机械收膜方面存在的主要问题是:地膜厚度小、强度差,增加了机具作业难度;现有机具的适配性单一,核心工作部件的可靠性不高,并且机收成堆(条)的地膜转运困难,后续处理工艺不完善,降低了农户的积极性。针对现有问题提出如下解决措施:1)研究人员在设计覆膜机具和残膜回收机具时应当与农艺相结合,改善机具作业效果及自身可靠性;2)提高我国农用塑料地膜质量,加快可降解地膜的研制。综上,加快研发优质可靠的覆膜、收膜机械是拓宽覆膜种植技术应用领域、提高覆膜地区机械化水平的重要保障。
Researches on the domestic mechanization of plastic film collection were systematically summarized in this study.The structure characteristics and working principle of two typical machines (plastic film mulching planter and collecting machine) were analyzed and compared in detail,and the existing problems in the current applied technology of plastic film mechanization were summarized and dissected.The major problems in plastic film mulching mechanical technology are high cavity rate and low emergency rate caused by the dislocation between seedling and plastic film and the uneven of soil covering and unreliable dibbling mechanism.Generally,two problems should be emphasized in mechanically collecting plastic film:Firstly,the film is too thin and the poor strength of current used plastic film increased operation difficulty in using machine.Secondly,the single suitability of existing machine and low reliability of key working component causes difficulty in transporting of strip residual plastic film collected by machine and incomplete follow-up treatment reduced farmers' enthusiasm.Corresponding solutions were proposed to solve these problems:1) To improve the working effect and reliability of machine,design of plastic film mulching planter and collecting machine should reference to agronomic requirements;2) Improve the quality of agricultural plastic film and accelerate the development of biodegradable film.In conclusion,research on and development of the plastic film mulching machine and collecting machine of better quality and higher reliability are important guarantees to broaden the application field of plastic film mulching technology and improve the level of mechanization.
碎石桩加固不同密实度液化土的孔隙水压力变化规律探讨
,郭英,吴永娟,张明
工程力学 , 2010,
Abstract: 通过碎石桩加固液化模型土振动台试验,研究了一定埋深时密实度变化的模型地基土振动过程中孔隙水压力和孔压比的峰值、振动结束后消散程度,揭示了加固与未加固液化土随埋深变化的孔压比与密实度的变化规律,阐明碎石桩加固液化土主要以密实度和排水两因素为主的加固机理,研究结果对今后实际工程碎石桩加固复合地基液化土判断有一定指导意义。
运用FLAC3D对水泥土桩加固液化砂土地基的分析
,刘峰,郭英,刘少文
工程力学 , 2013, DOI: 10.6052/j.issn.1000-4750.2012.03.S010
Abstract: 该文运用三维有限差分软件FLAC3D(FastLagrangianAnalysisofContinua)对水泥土桩加固的液化砂土地基建立模型并进行地震响应分析,从计算机数值模拟的角度对水泥土桩加固模型地基竖向位移、超静孔隙水压力、孔压比、剪应变增量、接触面剪力及表面加速度作了较系统地分析,总结了这些参数的变化规律,得到了一些有价值的结论,对实际工程有一定的指导意义。
河北北部偏远农村留守中小学生心理健康状况调查分析 
王瑞学, 朱莉,嗣霞
吉林大学学报(医学版) , 2012,
Abstract: 目的:调查河北北部偏远农村留守中小学生心理健康现状,阐明农村留守中小学生存在的心理问题及其影响因素,为制定有效干预措施提供依据。方法:采用整群分层抽样的方法,抽取河北省北部偏远地区留守学生超过在校学生50%的5所中学和2所小学中的2 040名10~16岁中小学生,运用自制一般情况问卷、心理健康诊断测验(MHT)量表进行问卷调查,分析父母外出打工对留守中小学生心理健康状况的影响。结果:北部偏远农村中小学生留守率为65.69%,农村留守中小学生心理健康状况较差,心理健康问题的检出率为34.50%,非留守学生检出率为14.50%,组间比较差异有统计学意义(P<0.05);父母双方均外出打工的留守中小学生心理症状检出率(38.23%)高于父母单方外出打工的留守学生(29.09%),差异有统计学意义(P<0.05);多因素Logistic回归分析,母亲单方打工和父母双方打工是留守中小学生心理健康问题的危险因素。结论:留守中小学生易发生心理问题,提示留守中小学生心理健康问题值得社会重视。
基于安全与纠错算法的增强型蓝牙基带研究与实现
李振荣,庄奕,张博,玉峰?
计算机科学 , 2010,
Abstract: 基于蓝牙在安全、纠错和杭干扰方面的不足,分析和改进了蓝牙协议数据链路层的跳频和纠错算法。分析了基于高级加密标准(aes)迭代型分组密码算法构造的新型跳频序列的性能,仿真结果表明该序列具有良好的安全性、均匀性和相关性。针对蓝牙dm分组,采用了融合交织编码和前向纠错的增强型纠错机制,并基于gillbert-elliott信道模型进行了仿真。结果表明该增强型纠错机制大大提高了数据传输的抗干扰能力。提出了基于aes的跳频序列发生器和融合交织编码的增强型纠错机制的asic实现结构,并运用低功耗和资源优化技术,给出了vlsi实现结果。基于改进算法ip,实现了高安全、强纠错的增强型蓝牙基带,并结合标准蓝牙基带进行了性能分析。最后,采用基于平台的设计方法,搭建了蓝牙soc系统平台,并进行了实测。
从词汇量角度再探汉语婴儿是否存在“名词优势”
陈永香,,朱莉
- , 2016,
Abstract: 摘要: 本研究采用交叉聚合设计,从词汇量角度考察了两岁左右汉语婴儿是否存在“名词优势”现象。在前测中,110名18、24和30个月龄的儿童接受了PCDI量表和父母问卷调查;6个月后,18个月和24个月组接受了PCDI量表的再测。本研究将“名词优势效应”定义为“(名词得分–动词得分)/词汇总分”(以k值表示),将名词得分大于动词得分者定义为“名词优势者”。结果发现:(1)从各年龄组均值来看,18个月组名词优势效应较小(k = .07),24及30个月组名词优势效应显著增大(k = .11~.19)。(2)从个体水平来看,18个月组名词优势者和动词优势者约各占50%(p > .05),而24、30个月组中81~100%的儿童都是名词优势者。该结果提示,以往不同研究之间的分歧可能是由于名词优势是随年龄而动态变化的。
Abstract: Most previous studies found that nouns were acquired predominantly by infants in many languages, thus noun bias was considered to be universal in children's early word learning. On the contrary, verbs were more difficult for children to learn, as they were less concrete and more relational than nouns. However, whether Mandarin Chinese is a verb-friendly language for children or not is still in hot debate. Evidences from natural observations and laboratory investigations were conflict. Researches that used vocabulary checklist found that Mandarin-speaking infants learnt many more verbs than their English-speaking peers did (Tardif, 1996). In the meanwhile, some experimental study found that Chinese children met more difficulties in verb learning tasks than English and Japanese children even in preschool years (Imai, et al., 2008). To further explore the noun/verb bias problem in Mandarin-speaking infants, it is proposed that the ratio of nouns and verbs should be carefully examined in the present study. As it is possible that the ratio of nouns and verbs might vary with children's age. In this study, Mandarin-speaking infants' expressive vocabulary size was examined to explore the ratio of nouns and verbs in a 6-month longitudinal study. In the first investigation, a sample of 110 infants were divided into three age groups, 18-, 24- and 30- month olds. All infants were tested using PCDI (Chinese Communicative Development Inventory - Putonghua Version) and a self-designed questionnaire for parents. The 18- and 24- month olds were re-tested after 6 months, using PCDI. In the present study, the Noun Bias Effect was defined as "(noun vocabulary size - verb vocabulary size)/whole vocabulary size", the result of this calculation was labeled as k. The results indicated that the noun bias effect was small in 18 month old group (k = .07), but it soon enlarged in 24- and 30- month olds (k = .11~.19). In the individual level, we defined the Noun Bias Infants as they learned more nouns than verbs. The results showed that the noun bias infants and the verb bias infants respectively constituted 50% of the whole sample in 18 month old group (p > .05). However, with the increase of age, most
Page 1 /16018
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.