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Search Results: 1 - 10 of 55053 matches for " 涂春?? "
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小系统的非平衡统计力学与随机热力学

物理 , 2014,
Abstract: ?热力学是一个古老的课题,古典热力学以宏观的具有大粒子数的系统为研究对象,自17世纪以来,科学家们构建了热力学的完备公理化体系。将热力学推广至小系统是近三十年来的研究前沿。文章介绍小系统的非平衡统计力学以及小系统的随机热力学。作为研究案例,利用时间依赖的谐振子势场控制单个粒子来构造随机热机的类卡诺循环,并发现该热机最大功率对应的效率等于1-,其中tc和th分别对应于低温热库和高温热库的温度。
边缘化“危机”与边缘化“意识”——论“五四”参照系中当代知识分子的“边缘化”
王玉,鸿?
天府新论 , 2009,
Abstract: 知识分子的"边缘化"包含着两层不同的含义,即边缘化"危机"与边缘化"意识",这是当代知识分子对自身的生存与发展基于两种不同语境的思考,看似自相矛盾,实则殊途同归。对"边缘化"的探讨意味着知识分子对自身角色的重新审视,以及对自己社会、历史位置的重新确定。而作为中国知识分子精神源头的"五四",无疑为当代知识分子自身合法性的建立提供了历史的精神资源与价值参照系。
外壁破裂对油菜小孢子胚胎发生影响的显微观察
Ultrasturctural Studies on Broken Exine Roles for Microspore Embryogenesis in Brassica napus L.cv. Topas
 [PDF]

金华, 万佳馨, 何宇清, 汤行
Botanical Research (BR) , 2016, DOI: 10.12677/BR.2016.53014
Abstract: 前期研究表明,油菜裂外壁小孢子也能胚胎发生。本研究以油菜裂外壁小孢子为材料,利用超微结构显微观察了破裂的外壁对胚胎发生的影响。结果表明,裂外壁小孢子可表现出与合子相似的某些结构特征;与合子进行不均等分裂而形成形态、结构迥异的顶基细胞类似,裂外壁小孢子也可以进行不均等分裂,形成大小和结构不同的两个子细胞。这些结果暗示破裂的外壁在小孢子极性生长和启动胚胎发生过程中重要作用。
In prior studies, the exine-dehisced microspore could also embryogenesis. Early events in micro-spore embryogenesis, such as polarity establishment, cell wall development, and the first division plane decision were investigated to reveal the mechanism controlling the process. In this paper, ra-peseed exine-dehisced microspores were used to reveal the roles of exine for microspore embryo-genesis by ultrastructural observation. The results show that some ultrastructural characteristic of the microspore is comparable to that of zygote, and that the dividing behavior of some exine-de- hisced microspore is similar to that of zygotes which could divide asymmetrically, resulting in two different daughter cells. This observation suggested that broken exine may play an important role in the polarity establishment during microspore embryogenesis.
成矿流体来源δD-δ18O-87Sr/86Sr理论模型研究
,光炽
中国科学 地球科学 中国科学 地球科学 , 1996,
Abstract: ?利用δD-δ18O-87Sr/86Sr封闭-静态多元同位素平衡分馏水/岩交换理论模型,对新疆阿尔泰多拉纳萨依强烈热液交代金矿床成矿流体的可能来源及其特征进行了理论模拟计算,结果表明成矿流体为变质热液、水-岩交换温度区间大致为250~350℃并且有效累积水/岩质量单位比较高(w/R(>>)1),该金矿床的形成可能与晚古生代末阿尔泰碰撞造山阶段在弧后扩张盆地中发育的有限相系浅变质作用有直接的成因关系。
汞对毛苕——根瘤菌共生固氮的影响
安千,
环境科学学报 , 1984,
Abstract: 本文以浓度梯度法研究了重金属离子二价汞对豆科根瘤菌和寄主毛苕生长结瘤固氮酶活性的影响。研究表明,根瘤菌各菌株间对Hg2+的忍耐程度有差异。当Hg2+浓度为2ppm时,多数菌株仍能正常生长;5ppm时,受不同程度的抑制;10ppm时,受到严重抑制,有些菌株完全不能生长;20ppm以上,所有供试菌株完全不能生长。在水培条件下,当Hg2+达10ppm、土培为50ppm时,毛苕的结瘤固氮受影响;水培20ppm、土培200ppm以上时,植物根部完全不
一种电力有源滤波器电流控制的新方法
唐欣,罗安,
电力系统自动化 , 2004,
Abstract: 针对电力有源滤波器存在滤波效果不够理想这一问题,并根据系统参考信号是周期变化的特点,提出了递推积分PI积分控制算法,实现对系统的无差控制。在此基础上,为提高系统响应速度,将递推积分PI控制与滞环控制有机结合,提出了复合型滞环控制方法。该方法具有计算量小、容易工程实现的特点。利用频域分析法从理论上证明了所提出的控制算法的有效性。最后,对所提出的方法和传统的滞环控制方法进行了仿真和实验研究,从快速性和控制精度2个方面进行了比较,验证了所提出的方法的可行性。
导电聚合物超级电容器电极材料*
亮亮,
化学进展 , 2010,
Abstract: 导电聚合物(聚苯胺,聚吡咯,聚噻吩)作为超级电容器电极材料的研究引起了人们广泛的兴趣,该类材料制备的超级电容器具有成本低、容量高、充放电时间短、环境友好和安全性高等优点。本文综述了近年来基于导电聚合物及其与无机材料(碳材料/金属氧化物材料)复合所得电极材料在超级电容器中的应用进展,指出具有纳米结构导电聚合物材料及导电聚合物与无机纳米材料的复合是超级电容器电极材料研究的重要发展方向。
节理岩体抗力系数的各向异性特征与计算方法
洪亮,,朱举
- , 2019, DOI: 10.11918/j.issn.03676234.201712022
Abstract: 隧道设计的荷载-结构法中,围岩抗力系数是影响衬砌内力与变形的重要参数,节理的存在会导致抗力系数的各向异性,然而,目前工程中较少考虑抗力系数的各向异性问题.以大连地铁2号线兴工街站隧道工程为背景,针对含有两组贯通节理岩体抗力系数的各向异性分布特征,采用正交试验和离散元数值模拟,分析岩石弹性模量、泊松比、节理间距、节理倾角、节理法向刚度等10个影响因素作用下抗力系数的分布规律.结果表明:洞周围岩抗力系数分布曲线呈椭圆形,长轴沿两组节理夹角角平分线方向;方差分析中5%水平下的显著性影响因素依次为节理法向刚度、岩石弹性模量、节理间距与节理倾角;各向异性系数随洞径与节理间距比值的增大呈现出先增大后减小的规律,当比值趋近于零或无穷大时,各向异性系数收敛于1.基于上述分析结果,进一步推导出围岩抗力系数椭圆分布函数的理论计算公式,并验证公式的准确性.工程实例计算表明,围岩抗力系数的各向异性对衬砌轴力的影响较小,对弯矩的影响显著.
In load-structure model for tunnel design, the rock mass resistant coefficient (k) is an important parameter which affects the behavior of the tunnel structure prominently. The anisotropy of k appears due to the presence of joints. However, no adequate efforts have been made to research the anisotropic distribution of k in jointed rock masses. Ten influencing factors including the elastic modulus of rock, Poisson’s ratio, and the properties of two sets of joints were analyzed for evaluating the anisotropic distribution of k, by using orthogonal array testing strategy (OATS) and distinct element method (DEM), with Xinggongjie Station Tunnel Project on No. 2 Line of Dalian Metro as an example. The results show that the distribution curves of k were oval-shaped. The maximum value was along the direction of the two joints angle bisector. Using the variance analysis of OATS, the significant influencing factors at the level of five percent were the elastic modulus of the rock, the normal stiffness of the joints, the spacing of the joints, and the intersection angle of two sets of joints. With the increase of the ratio of tunnel diameter to joint spacing, the anisotropy coefficient of k increased first and then started to drop, which converged to one when the ratio was equal to zero or infinite. Based on the above analysis results, the elliptic function of k was derived and was verified. The engineering example shows that the resistant coefficient of jointed rock mass is obviously anisotropic, which has little influence on the axial force of lining and remarkable influence on bending moment.
龙凤山和瓦里关臭氧总量异常变化与天气过程关系研究
Variations in Total Ozone Observed at Longfengshan and Waliguan and Its Relationship with Synoptic Process

小林,郑向东,
- , 2015, DOI: 10.13209/j.0479-8023.2015.003
Abstract: 摘要 通过对黑龙江龙凤山和青海瓦里关Brewer 地基臭氧总量的长期观测资料以及与观测时段对应的全球 NCEP R1 系列位势高度再分析资料的统计分析发现, 龙凤山和瓦里关臭氧总量观测值有时存在剧烈的逐日变化, 对这种异常变化进行定量分析, 并对其与对流层天气过程的关系进行研究, 发现两者之间存在良好的对应关系。臭氧总量的异常变化大多数出现在11 月至次年5 月的冬、春季节, 并且臭氧总量的异常升高(第一类异值点)总是伴随着平流层低层(250~70 hPa)的槽线和地面(1000 hPa)的低压中心后方的天气形势, 而臭氧总量的异常降低(第二类异值点)则时常伴随平流层低层的脊线和地面的高压中心后方的天气形势, 这表明臭氧总量的异常变化可以作为地面天气系统转变的一个信号。
Abstract Longtime in-situ measurements of total ozone from the ground-based Brewer observatories at Longfengshan in Heilongjiang Province and Waliguan in Qinghai Province were analyzed together with the according geopotential height data from NCEP R1 reanalysis series. Abnormal day-to-day fluctuations in the total ozone amount were found at times, which were analyzed in respect to synoptic processes. Results show that the impact of synoptic conditions is highly related to the variation of the total ozone amount. The anomaly in total ozone amount mostly appears in winter and spring (from November to May in the following year). The abnormal high total ozone amounts (the first kind of abnormal data points) always occur when the station is at the rear of the near surface (1000 hPa) cyclone with a simultaneous air pressure trough approaching in lower stratosphere (250 to 70 hPa). The abnormal low total ozone amounts (the second kind of abnormal points) always occur when the station is behind a near surface anticyclone with a simultaneous air pressure ridges approaching in lower stratosphere. The anomaly in total ozone amount can be considered as a signal for the upcoming transition between near surface cyclone and anticyclone.
新型注入式HAPF谐波电流及直流侧电压控制新方法
赵伟,罗安,彭建,
中国电机工程学报 , 2008,
Abstract: 针对注入式混合有源滤波器中无源与有源部分补偿效果叠加、补偿谐波电流在经过注入支路和输出滤波器之后会产生一定的相位和幅值偏差,以及基波谐振支路的存在使得必须通过添加整流桥的方式获取直流侧电压从而难以保持直流侧电压的稳定等问题,提出了一种改进结构的新型谐振注入式混合型有源滤波器(hybridactivepowerfilter,HAPF),使直流侧电容能够与电网产生能量交换。在此基础上结合提出的基于基波无功电流闭环调节的直流侧电压控制方法,保证了直流侧电压的稳定;提出了采用递推积分将无源滤波器作用后电网谐波电流与注入支路补偿电流进行闭环比较控制以获得参考电流的方法,减小了误差,提高了系统的控制精度。实验及仿真结果证明了所提出控制方法计算量较小,在响应时间和控制精度上都具有一定优势,能够满足系统的要求。
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