oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 23 )

2018 ( 456 )

2017 ( 554 )

2016 ( 509 )

Custom range...

Search Results: 1 - 10 of 24405 matches for " 叶辰 "
All listed articles are free for downloading (OA Articles)
Page 1 /24405
Display every page Item
中国贫困县划分精度商榷—基于夜间灯光数据的检验
Is the Poverty Evaluation of National Poverty County Accurate—A Evaluation based on the Night-time Light


- , 2018,
Abstract: 精准识别贫困对象是客观、科学进行扶贫的重要基础。20世纪90年代以来,我国经历了扶贫开发的三个阶段,确定了592个国家级贫困县。 评定过程受到哪些因素的影响等,都是需要正视的问题。 基于此,文章使用 DMSP / OLS 夜间灯光数据,对贫困县的评定结果进行检验与分析。 研究发现:总体上非弱夜间灯光密度的贫困县数超过四成,这一偏误具有地区差异性;产生偏误的主要原因是“老少边”政策因素与领导人“关系上的照顾”产生的交互作用。
The accurate poverty evaluation is an important basis for objective and scientific poverty alleviation. Since 1990s, China has gone through three stages of poverty alleviation and identified the state-level poverty-stricken county. Whether the evaluation result is objective, fair and reasonable, it is a problem that needs to be squarely faced. Based on this, we use DMSP / OLS night-time light to test and analyze the evaluation results of the national poverty county. We find that (1) in general, the number of the national poverty county with non-weak average night-time light has been over 40%. (2) The biased errors of the poor evaluation in the northeast, western and central regions are more obvious. (3) The main reason for the biased errors is the interaction between the policy factors which take care of the old revolutionary base areas, minority nationality regions as well as frontier areas, and the leade’爷s factors.
参强联合作用非线性结构动力学实验建模
,
力学学报 , 2013, DOI: 10.6052/0459-1879-12-174
Abstract: 搭建以L型梁为实验研究对象的参强联合作用多自由度非线性振动实验系统,将增量谐波平衡非线性识别理论运用到实验建模方法中,建立了L型梁的动力学控制方程.通过对不同激励频率和不同响应情况下的数值模拟与实验数据的比较,验证了基于增量谐波平衡识别的实验建模方法对多自由度参强联合作用非线性动力学结构的有效性,以及动力学控制方程的普适性.
镰刀菌李瑟组研究——Ⅱ.镰刀菌李瑟组的分类性状评价及其种类*
王拱,鲍建荣,琪明
微生物学通报 , 1992,
Abstract:
聚富马酸丙二醇酯/羟基磷灰石复合多孔水凝胶的制备及其矿化性能研究
,李振华,李丹,高长有
高分子学报 , 2012, DOI: 10.3724/SP.J.1105.2012.12129
Abstract: 采用二步法合成了可降解的聚富马酸丙二醇酯(poly(propylenefumarate),PPF),并和N-乙烯基吡咯烷酮(N-vinylpyrrolidone,NVP)共聚,以1,4-二氧六环为溶剂,通过改变溶剂的量制备了溶胀性能不同的PPF水凝胶.采用万能力学测试仪和扫描电子显微镜分别表征了水凝胶的压缩模量和形貌结构.选择20%PPF和10%NVP的聚合体系,预掺3%的纳米羟基磷灰石(hydroxyapatite,HA),以氯化钠粒子为致孔剂,制备了孔径在280~450μm的纳米复合多孔水凝胶,使其压缩模量提高了61%.模拟体液矿化10天的结果显示,磷灰石成核位点的存在和良好的与外界液体环境物质交换的能力,促进了多孔水凝胶表面磷灰石的沉积,说明HA的复合可以有效提高PPF多孔水凝胶的成骨活性.
雨水中有机酸的离子色谱法测定
汝求,,吴小蔚
环境化学 , 2015,
Abstract: 本文研究了以邻苯二甲酸为淋洗液,用无抑制柱离子色谱仪测定甲酸、乙酸、丁二酸、乳酸一氯乙酸、苯甲酸、抗坏血酸和果糖酸等有机酸的条件,确定了淋洗液的pH值对色谱峰保留时间和响应值的影响。当pH为4.15时,分离效果很好,可同时测定六种有机酸,但pH值在3—4范围内,色谱峰高随pH值的增高而降低。本方法可测定浓度为ppm量级的有机酸,精密度良好,变异系数一般在3%以下,检测限在0.05μg/ml(甲酸)至0.70μg/ml(抗坏血酸)之间。本法可用于测定雨水中微量有机酸,雨水中常见的无机阴离子存在并不干扰测定。
一类二元相关威布尔分布的可靠性问题
汪美,慈南,徐冬元
应用概率统计 , 2006,
Abstract: 本文考虑生存函数为${\ol{F}(x_{1},x_{2})}=\exp\{-[(x_{1}^{1/\alpha}/\theta_{1})^{1/\delta}+(x_{2}^{1/\alpha}/\theta_{2})^{1/\delta}]^{\delta}\},\;x_{i}>0,\;\alpha>0$,$1\geq\delta>0,\;\theta_{i}>0\;(i=1,2)$的二元威布尔分布的两种可靠性问题,提出可靠度$\pr$的估计并讨论了它们的渐近性,最后还作了模拟计算.
塞式喷管模拟实验及数据采集系统
戴梧,刘宇?,程显
推进技术 , 2000,
Abstract: 为了了解塞式喷管性能,采用固体推进剂对塞式喷管单元发动机进行了模拟实验。重点介绍了塞式喷管单元发动机模拟实验的实验系统和高精度测量系统以及数据采集软件。同时,简单说明了数据处理的方法。最后给出了典型的实验结果,该结果对塞式喷管的设计、理论研究以及数值计算有重要的参考价值
“瓦”状塞式喷管的数值模拟与实验
戴梧,刘宇?,马彬?,程显
推进技术 , 2002,
Abstract: 为了寻求高性能和更接近工程应用的发动机,提出了一种内喷管为轴对称喷管、塞锥为凹面的“瓦”状塞式喷管,分析了这种塞式喷管的优缺点,并针对一研究模型进行了数值模拟和实验比较。数值模拟采用nnd格式求解曲线坐标下的三维平均雷诺的ns方程,并用kε两方程湍流模型封闭方程组;实验研究采用酒精和氧气作为推进剂进行了热试车;研究模型的内喷管面积比为324,总膨胀比为2215,设计压力比为220。结果显示“瓦”状塞锥改善了塞锥的流场,并且当压力比在168~220的范围内变化时,其相对理想喷管的喷管效率在090~096内变化。对发动机设计作进一步改进,其性能有望进一步提高
一类跳扩散过程下期权定价公式的参数估计
刘睿,刘国祥,
南京师范大学学报(自然科学版) , 2014,
Abstract: 对于参数为常数的跳扩散过程模型下的期权公式,本文给出了较为方便的利用历史数据计算其参数的极大似然估计.
石墨烯转移工艺对石墨烯传感器检测汞离子的影响
李小晴,,林正得,江南
- , 2018, DOI: 10.11951/j.issn.1005-0299.20170363
Abstract: 本工作采用化学气相沉积法(CVD)石墨烯制备场效应晶体管(FET)传感器,在石墨烯表面修饰DNA,用于检测汞离子.为探索转移方法对石墨烯传感器件性能的影响,制备了3种不同转移工艺的石墨烯样品,分别是PMMA转移方法中退火烧除PMMA的石墨烯、用丙酮洗去PMMA的石墨烯和Au转移的石墨烯,对石墨烯样品进行拉曼光谱、分光光度计、光学显微镜(OM)、扫描探针显微镜(SPM)的表征.通过FET转移特性曲线的输出,得到汞离子对石墨烯掺杂情况的变化,从而考察了各种石墨烯传感器对汞离子的检测性能.结果表明,Au转移的石墨烯表面清洁程度最佳,SPM图像显示其表面平坦无杂质,表面粗糙度(Ra)仅为0.45 nm.用该种石墨烯制备的传感器件对汞离子检测的检测限达10 pM,且FET的狄拉克点变化也最大,达-0.132 V.
In this work, chemical vapor deposition (CVD) graphene was decorated with DNA to fabricate field effect transistor (FET) sensors for mercury ion detection. To figure out the effects of different samples on the detection of Hg2+, this study exploited three different samples:the sample on which PMMA was burned, the sample on which PMMA was washed by acetone and the sample which was transferred by Au. The quality of the graphene was characterized by Raman spectroscopy, spectrophotometer, optical microscope as well as scanning probe microscopy. Three different devices were fabricated by corresponding samples.Through the FET transfer curves, different doping conditions of graphene were obtained, and the detetion performance of various graphene sensors was investigated. It was shown that the sample which was transferred by Au had the cleanest surface. In the corresponding device, the detection limit of Hg2+ could achieve 10 pM, and the change of Dirac point was the largest which was up to -0.132 V.
Page 1 /24405
Display every page Item


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