期刊文献+
共找到20篇文章
< 1 >
每页显示 20 50 100
北京地区鸟类区系初探 被引量:1
1
作者 傅必谦 陈卫 高武 《河北大学学报(自然科学版)》 CAS 1996年第S1期36-40,共5页
依据1983—1993年的调查资料,初步分析了北京地区鸟类区系的特征和华北两个亚区在北京的分界线。提出北京鸟类区系具有比较浓厚的北方鸟类区系和季风区鸟类区系的特点,位于华北区两个亚区接界处的特征也十分突出,且与东北区长白山亚区... 依据1983—1993年的调查资料,初步分析了北京地区鸟类区系的特征和华北两个亚区在北京的分界线。提出北京鸟类区系具有比较浓厚的北方鸟类区系和季风区鸟类区系的特点,位于华北区两个亚区接界处的特征也十分突出,且与东北区长白山亚区和蒙新区东部草原亚区鸟类区系关系密切。初步建议将两个亚区的分界线划在张坊—长操—高崖口—长陵—石城—古北口—北庄—熊儿寨—靠山集一线。 展开更多
关键词 鸟类 北京地 分界
下载PDF
大锥段注气对液-液水力旋流器分离性能的影响 被引量:2
2
作者 陈德海 魏振禄 +1 位作者 蒋明虎 赵立新 《化工机械》 CAS 2014年第4期480-483,495,共5页
针对油田含聚污水处理难度大的问题,利用CFD和多孔介质模型建立了旋流器内部流体的计算模型,数值模拟分析了大锥段注气旋流器内多相流体速度场和压力场的分布规律,结果表明:大锥段注气后,在旋流区和大锥段区的径向速度和流向溢流口的轴... 针对油田含聚污水处理难度大的问题,利用CFD和多孔介质模型建立了旋流器内部流体的计算模型,数值模拟分析了大锥段注气旋流器内多相流体速度场和压力场的分布规律,结果表明:大锥段注气后,在旋流区和大锥段区的径向速度和流向溢流口的轴向速度明显提高,分离性能有所改善;产生的气浮选效应使混合液的分离难度降低,压力降减小,节约了能源。提出旋流器流场分界区的概念,研究表明在分界区注气能更好地改善分离效果,分界区的位置取决于旋流器的结构参数和操作参数。 展开更多
关键词 旋流器 大锥段注气 分离性能 数值模拟 分界区
下载PDF
Optimal Boundary Control Method for Domain Decomposition Algorithm
3
作者 闫桂峰 冯恩民 《Journal of Beijing Institute of Technology》 EI CAS 2000年第2期113-119,共7页
To study the domain decomposition algorithms for the equations of elliptic type, the method of optimal boundary control was used to advance a new procedure for domain decomposition algorithms and regularization method... To study the domain decomposition algorithms for the equations of elliptic type, the method of optimal boundary control was used to advance a new procedure for domain decomposition algorithms and regularization method to deal with the ill posedness of the control problem. The determination of the value of the solution of the partial differential equation on the interface——the key of the domain decomposition algorithms——was transformed into a boundary control problem and the ill posedness of the control problem was overcome by regularization. The convergence of the regularizing control solution was proven and the equations which characterize the optimal control were given therefore the value of the unknown solution on the interface of the domain would be obtained by solving a series of coupling equations. Using the boundary control method the domain decomposion algorithm can be carried out. 展开更多
关键词 domain decomposition methods(DDM) boundary control REGULARIZATION coupling equations
下载PDF
连铸钢板坯凝固壳横截面变形与内部裂纹的关系 被引量:3
4
作者 曾全胜 蒋云云 隋然 《理化检验(物理分册)》 CAS 2003年第6期290-294,共5页
对实际观察到的连铸钢板坯拉出结晶器时的横截面形状与最终形成的内部裂纹进行了理论分析 ,找到了凝固壳横截面形状变化与内部裂纹的形成及种类之间的因果关系及规律性 ,为预防连铸钢板坯内部裂纹提供了理论依据。同时对YB/T 4 0 0 3- 1... 对实际观察到的连铸钢板坯拉出结晶器时的横截面形状与最终形成的内部裂纹进行了理论分析 ,找到了凝固壳横截面形状变化与内部裂纹的形成及种类之间的因果关系及规律性 ,为预防连铸钢板坯内部裂纹提供了理论依据。同时对YB/T 4 0 0 3- 1991标准中的有关问题进行了讨论 。 展开更多
关键词 连铸钢板坯 凝固壳 横截面变形 内部裂纹 拉应力 中心裂纹 局部凹陷 偏析 三角分界裂纹
下载PDF
Phosphate Distribution and Movement in Soil-Root In-terface Zone:Ⅲ.Dynamics 被引量:2
5
作者 XUMING-GANG ZHANGYI-PING 《Pedosphere》 SCIE CAS CSCD 1995年第4期349-355,共7页
The depletion rate of phosphate in the soil-root interface zone increased along with growth and phosphateuptake of wheat or maize, which indicated that the phosphate distribution in soil near the root surfaceagreed we... The depletion rate of phosphate in the soil-root interface zone increased along with growth and phosphateuptake of wheat or maize, which indicated that the phosphate distribution in soil near the root surfaceagreed well with the phosphate movement in rhizosphere and phosphate uptake by plant. The relativeaccumulation zone of phosphate within 0.5 mm apart from the root surface developed at the 15th day or soafter cultivating wheat or maize since the root phosphate secretion increased gradually in this stage. Thephosphate distribution in the soil-root interface zone against the growing time (t) and the distance from theroot plane (x) could be described by the non-linear regression equation with the third powers of x and t. 展开更多
关键词 DYNAMICS phosphate distribution soil-root interface zone
下载PDF
Flotation bubble image segmentation based on seed region boundary growing 被引量:4
6
作者 Zhang Guoying Zhu Hong Xu Ning 《Mining Science and Technology》 EI CAS 2011年第2期239-242,共4页
Segmenting blurred and conglutinated bubbles in a flotation image is done using a new segmentation method based on Seed Region and Boundary Growing(SRBG).Bright pixels located on bubble tops were extracted as the se... Segmenting blurred and conglutinated bubbles in a flotation image is done using a new segmentation method based on Seed Region and Boundary Growing(SRBG).Bright pixels located on bubble tops were extracted as the seed regions.Seed boundaries are divided into four curves:left-top,right-top,right-bottom, and left-bottom.Bubbles are segmented from the seed boundary by moving these curves to the bubble boundaries along the corresponding directions.The SRBG method can remove noisy areas and it avoids over- and under-segmentation problems.Each bubble is segmented separately rather than segmenting the entire flotation image.The segmentation results from the SRBG method are more accurate than those from the Watershed algorithm. 展开更多
关键词 Bubble image SEGMENTATION Seed area Region growing
下载PDF
辅料取料机自动控制系统的设计与安装、调试 被引量:1
7
作者 李大庆 周富豪 +3 位作者 汪江杰 苏国志 蓝华勇 王利荣 《中国水泥》 CAS 2021年第6期115-118,共4页
在简述辅料取料机自动控制系统技改项目立项原因及提出技术要求、需要实现功能基础上,介绍了辅料取料机自动控制系统的电路与程序的设计思路及安装调试方法,同时列举了可能出现的问题,作为此类系统的成功案例,对同行具有一定参考意义。
关键词 辅取 堆场 分界 位置坐标
下载PDF
Distribution area demarcation for logistic centers under geographical information system decision support system
8
作者 潘文安 《Journal of Chongqing University》 CAS 2011年第1期14-22,共9页
Demarcating distribution area of goods is often guided by the rule of thumb by business proprietors. However, this method seems to be unsuitable when the demand points increase to a certain large extent. The present w... Demarcating distribution area of goods is often guided by the rule of thumb by business proprietors. However, this method seems to be unsuitable when the demand points increase to a certain large extent. The present work attempted to convert the problem of distribution area demarcation into a localized problem of warehouseing and networking, and tried to establish district-based planning mode based on location based heuristic (LBH). Two methods were used in this study: 1) the manual method to construct the mathematical model and conduct simulation; 2) the automatic method using TransCAD software of geographical information system (GIS) for simulation. By comparing the effects of the two methods, the research provides theoretical support for business proprietors to demarcate the distribution area rationally with the application of GIS system. The results show that GIS has very good graphics construction function to replace complex text, and the automatic demarcating mode with human-machine interaction provides a good business decision-making support. 展开更多
关键词 distribution area demarcation decision support system geographical information system
下载PDF
The Relationship Between Strong Earthquake Activity of M_S≥7.0 on the Chinese Mainland and the West Kunlun-A'nyêmaqên Secondary Arcuate Tectonic Zone
9
作者 ZhangXiaodon WangHuimin LuMeimei YuSurong 《Earthquake Research in China》 2004年第2期171-177,共7页
The active and quiet phenomenon of moderate strong earthquakes one year before the earthquakes with M S≥7.0, the spatial distribution characteristics of the solid tide modulating and triggering earthquakes and the st... The active and quiet phenomenon of moderate strong earthquakes one year before the earthquakes with M S≥7.0, the spatial distribution characteristics of the solid tide modulating and triggering earthquakes and the strong earthquake mechanisms on the Chinese continent have been studied. The secondary arcuate tectonic zone composed of the west Kunlun-Anyêmaqên faults is believed to be a very important boundary to characterize strong earthquake activity of M S≥7.0 on the Chinese continent, that is, a boundary between the seismically active region and the quiet region of moderately strong earthquakes one year before earthquakes with M S≥7.0, and a boundary of the spatial distributions between the solid tide modulating strong earthquakes (M S≥7.0) and the non-modulating ones. It might be related with the characteristics of spatial distribution of focal mechanism solutions of strong earthquakes on the Chinese Continent. 展开更多
关键词 Arcuate tectonic zone Boundary zone Strong earthquake Seismicity characteristics
下载PDF
Thermodynamics of Third Order Lovelock Anti-de Sitter Black Holes Revisited
10
作者 ZOU De-Cheng YUE Rui-Hong YANG Zhan-Ying 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第3期449-456,共8页
We compute the mass and temperature of third order Lovelock black holes with negative Gauss-Bonnet coefficient a2 〈 0 in anti-de Sitter space and perform the stability analysis of topological black holes. When k = -1... We compute the mass and temperature of third order Lovelock black holes with negative Gauss-Bonnet coefficient a2 〈 0 in anti-de Sitter space and perform the stability analysis of topological black holes. When k = -1, the third order Lovelock black holes are thermodynamically stable for the whole range r+. When k = 1, we found that the black hole has an intermediate unstable phase for D = 7. In eight dimensional spacetimes, however, a new phase of thermodynamically unstable small black holes appears if the coefficient a is under a critical value. For D ≥ 9, black holes have similar the distributions of thermodynamically stable regions to the case where the coefficient & is under a critical value for D = 8. It is worth to mention that all the thermodynamic and conserved quantities of the black holes with fiat horizon do not depend on the Loveloek coefficients and are the same as those of black holes in general gravity. 展开更多
关键词 third order Lovelock gravity AdS space THERMODYNAMICS
下载PDF
Phosphate Distribution and Movement in Soil-Root In-terface Zone:I. The Influence of Transpiration Rate 被引量:1
11
作者 XUMING-GANG ZHANGYI-PING 《Pedosphere》 SCIE CAS CSCD 1995年第2期115-126,共12页
The experiments were conducted in the artificial climate laboratory using  ̄(32)P labelled soil and soil-rootplane system to investigate phosphate distribution and its movement in the soil-root interface zone andtheir... The experiments were conducted in the artificial climate laboratory using  ̄(32)P labelled soil and soil-rootplane system to investigate phosphate distribution and its movement in the soil-root interface zone andtheir relations with phosphate uptake by plant as well as transpiration rate (atmosphere humidity). It wasfound that although the phosphate in the soilroot interface zone was of depletive distribution as a functionC/Co = ax ̄b(C/Co is the relative content of fertilizer phosphate in a distance from the root surface x, aand b are the regression constants), and a relative accumulation zone of phosphate within 0.5 mm near theroot surface was often observed especially in the heavier texture soils because of root phosphate secretion.The depletion intensity of phosphate in the soil-root interface zone was in agreement with the phosphateuptake by plants under two humidities very well. However, the effects of air humidity on characteristics ofthe phosphate distribution near wheat or maize root surface were different. Wheat grew better under loweratmosphere humidity while maize, under higher humidity, which caused a more intensive uptake and thusa stronger depletion of phosphate in the rhizosphere. Moreover, the depletion intensity was greater by thebottom or the middle part of wheat roots and by the top or the middle part of maize roots. The depletivedistribution of phosphate in the rhizosphere soil and the relative contribution of phosphate diffusion to plant,which was more than 98% in the cultural experiments, indicated that diffusion was a major process forphosphorus supply to plants. 展开更多
关键词 phosphate distribution soil-root interface zone transpiration rate
下载PDF
Improved Parallel Processing Function for High-Performance Large-Scale Astronomical Cross-Matching 被引量:2
12
作者 赵青 孙济州 +3 位作者 于策 肖健 崔辰州 张啸 《Transactions of Tianjin University》 EI CAS 2011年第1期62-67,共6页
Astronomical cross-matching is a basic method for aggregating the observational data of different wavelengths. By data aggregation, the properties of astronomical objects can be understood comprehensively. Aiming at d... Astronomical cross-matching is a basic method for aggregating the observational data of different wavelengths. By data aggregation, the properties of astronomical objects can be understood comprehensively. Aiming at decreasing the time consumed on I/O operations, several improved methods are introduced, including a processing flow based on the boundary growing model, which can reduce the database query operations; a concept of the biggest growing block and its determination which can improve the performance of task partition and resolve data-sparse problem; and a fast bitwise algorithm to compute the index numbers of the neighboring blocks, which is a significant efficiency guarantee. Experiments show that the methods can effectively speed up cross-matching on both sparse datasets and high-density datasets. 展开更多
关键词 astronomical cross-matching boundary growing model HEALPix task partition data-sparse problem
下载PDF
Role of hydro-geochemical functions on karst critical zone hydrology for sustainability of water resources and ecology in Southwest China 被引量:1
13
作者 Xi Chen Yimeng Sun Richao Huang 《Acta Geochimica》 EI CAS CSCD 2017年第3期494-497,共4页
Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction amon... Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized. 展开更多
关键词 Hydro-geochemical analysis Karst critical zone Water resources Vegetation Southwest China
下载PDF
The Effect on Sporadic-E of Quasi-Biennial Oscillation
14
作者 Ramazan Atici Selcuk Sagir 《Journal of Physical Science and Application》 2016年第2期10-17,共8页
In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at the equatorial stratosphere, and critical frequency of layer (Es) sporadically observed at the ionospheric E region wa... In this study, the relationship between the QBO (quasi-biennial oscillation), which is seen at the equatorial stratosphere, and critical frequency of layer (Es) sporadically observed at the ionospheric E region was analyzed by using multiple regression model. For this analysis, Es layer critical frequency (foEs) obtained from four different stations at equatorial region and QBO measured at 10 hPa altitude values were used. The positive relationship between foEs and QBO was observed at all stations. An increase of 1 m/s at QBO leads to an increase of 0.01 Mhz, 0.02 Mhz, 0.02 Mhz and 0.01 Mhz (Jicamarca, Ascension, Manila and Kwajalein) on foEs, respectively. Expect for Manila station, westerly phase of QBO has greater effect on foEs compared to easterly phase of QBO at all other stations. It is seen that the changes occurred on foEs can be explained by the QBO at rates 47%, 46%, 32% and 44% for Jicamarca, Ascension, Manila and Kwajalein stations, respectively. 展开更多
关键词 Sporadic E QBO multiple regression model ionospheric E-Region.
下载PDF
Investigation of Edge Fluctuation Characteristics on the HL-2A Tokamak
15
作者 HONG Wenyu YAN Longwen QIAN Jun LI Qiang ZHAO Kaijun CHENG Jun LUO Cuiwen XU Zhengyu HUANG Yuan 《Southwestern Institute of Physics Annual Report》 2005年第1期23-24,共2页
The edge plasma fluctuation characteristics are studied by the fast reciprocating scanning 6-probes in the boundary region. These probes can measure edge plasma temperature, density, poloidal electric field, radial el... The edge plasma fluctuation characteristics are studied by the fast reciprocating scanning 6-probes in the boundary region. These probes can measure edge plasma temperature, density, poloidal electric field, radial electric field, Reynolds stress, and their profiles in once discharges. Measurement results are used to analyze plasma confinement, turbulent fluctuations and their correlation characteristics during multi-shot pellet injection (MPI) , supersonic molecular beam injection (SMB1) and electron cyclotron resonant heating ( ECRH ) discharges. 展开更多
关键词 Fast-scanning probe Multi-shot pellet injection Supersonic molecular beam injection
下载PDF
Hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation of jet mixing in a supersonic crossflow 被引量:1
16
作者 WANG HongBo WANG ZhenGuo +1 位作者 SUN MingBo QIN Ning 《Science China(Technological Sciences)》 SCIE EI CAS 2013年第6期1435-1448,共14页
A sonic under-expanded transverse jet injection into a Ma 1.6 supersonic crossflow is investigated numerically using our hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) method. First, a calcula... A sonic under-expanded transverse jet injection into a Ma 1.6 supersonic crossflow is investigated numerically using our hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) method. First, a calculation is carried out to validate the code, where both the instantaneous and statistical results show good agreement with the existing experimental data. Then the jet-mixing characteristics are analyzed. It is observed that the large-scale vortex on the windward portion of the jet boundary is formed mainly by the intermittent impingement of the incoming high-speed fluid on the relatively low-speed region of the upstream jet boundary, where the interaction between the upstream separated region and the jet supplies a favorable pressure condition for the sustaining acceleration of the high-speed fluid during the vortex forming, associated with which the incoming fluid is entrained into the jet boundary and large-scale mixing occurs. Meanwhile, the secondary recirculation zone between the upstream separated region and the jet is observed to develop evidently during the vortex forming, inducing the entrainment of jet fluid into the upstream separated region. Moreover, effects of the incoming boundary layer on the jet mixing are addressed. 展开更多
关键词 hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) jet mixing SUPERSONIC boundary layer
原文传递
Numerical calculation and influencing factors of the volume fraction of interfacial transition zone in concrete 被引量:3
17
作者 SUN GuoWen SUN Wei +1 位作者 ZHANG YunSheng LIU ZhiYong 《Science China(Technological Sciences)》 SCIE EI CAS 2012年第6期1515-1522,共8页
The determination of volume fraction of interracial transition zone (ITZ) is very important for investigating the quantitative relationship between the microstructure and macroscopical property of concrete. In this ... The determination of volume fraction of interracial transition zone (ITZ) is very important for investigating the quantitative relationship between the microstructure and macroscopical property of concrete. In this paper, based on Lu and Torquato's most nearest surface distribution function, a calculating process of volume fraction of ITZ is given in detail according to the actual sieve curve in concrete. Then, quantitative formulas are put forward to measure the influencing factors on the |TZ vol- ume fraction. In order to validate the given model, the volume fractions of ITZ obtained by numerical calculation are compared with those by computer simulation. The results show that the two are in good agreement. The order of the factors influencing the ITZ volume fraction is the ITZ thickness, the volume fraction of aggregate and the maximum aggregate diameter for Fuller gradation in turn. The 1TZ volume fraction obtained from the equal volume fraction (EVF) gradation is always larger than that from the Fuller gradation for a given volume fraction of aggregate. 展开更多
关键词 CONCRETE interfacial transition zone (ITZ) volume fraction Fuller distribution equal volume fraction distribution(EVF) sieve curve
原文传递
The vertical distribution characteristics of integral turbulence statistics in the atmospheric boundary layer over an urban area in Beijing 被引量:7
18
作者 LIU Yang LIU HuiZhi WANG Lei 《Science China Earth Sciences》 SCIE EI CAS CSCD 2017年第8期1533-1545,共13页
Turbulence data(2008–2012) from a 325 m meteorological tower in Beijing, which consisted of three layers(47,140, and 280 m), was used to analyze the vertical distribution characteristics of turbulent transfer over Be... Turbulence data(2008–2012) from a 325 m meteorological tower in Beijing, which consisted of three layers(47,140, and 280 m), was used to analyze the vertical distribution characteristics of turbulent transfer over Beijing city according to similarity theory. The conclusions were as follows.(1) Normalized standard deviations of wind speeds/ui * were plotted as a function only of a local stability parameter. The values under near-neutral conditions were 2.15, 1.61, and 1.19 at 47 m, 2.39, 1.75,and 1.21 at 140 m, and 2.51, 1.77, and 1.30 at 280 m, showing a clear increase with height. The normalized standard deviation of wind components fitted the 1/3 law under unstable stratification conditions and decreased with height under both stable and unstable conditions.(2) The normalized standard deviation of temperature fitted the.1/3 law in the free convection limit, but was quite scattered with different characteristics under near-neutral conditions. The normalized standard deviations of humidity and the CO2 concentration fitted the.1/3 law under unstable conditions, and remained constant under near-neutral and stable stratification. The normalized standard deviation of scalars, i.e., temperature, humidity, and CO2 concentration, all increased with height.(3) Compared with momentum, and the water vapor and CO2 concentrations, the turbulence correlation coefficient for heat was smaller under near-neutral conditions, but larger under both stable and unstable conditions. A dissimilarity between heat, and the water vapor and CO2 concentrations was observed in urban areas. The relative correlation coefficients between heat and each of momentum, humidity, and CO2 concentration(|rwT/ruw|, |rwT/rwc| and |rwT/ruq|) in the lower layers were always larger than in higher layers, except for the relative correlation coefficient between heat and humidity in an unstable stratification. Therefore, the ratio between heat and each of momentum, humidity, and CO2 concentration decreased with height. 展开更多
关键词 Urban boundary layer Local similarity theory Integral turbulence statistics
原文传递
Chaotification of a Continuous Stable Complex Network via Impulsive Control
19
作者 LIU Na GUAN Zhihong 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2015年第6期1271-1278,共8页
A method is proposed to chaotify a class of complex networks via impulsive control, when the orbits of the impulsive systems are confined in a bounded area. Based on computing the largest Lyapunov exponent, theoretica... A method is proposed to chaotify a class of complex networks via impulsive control, when the orbits of the impulsive systems are confined in a bounded area. Based on computing the largest Lyapunov exponent, theoretical results and algorithmic analysis are given in details. Finally, numerical simulations are presented to illustrate the effectiveness of the method. 展开更多
关键词 CHAOTIFICATION complex network impulsive control largest Lyapunov exponent
原文传递
Interval analysis of transient temperature field with uncertain-but-bounded parameters
20
作者 WANG Chong QIU ZhiPing 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2014年第10期1959-1966,共8页
Based on the traditional finite volume method, a new numerical technique is presented for the transient temperature field prediction with interval uncertainties in both the physical parameters and initial/boundary con... Based on the traditional finite volume method, a new numerical technique is presented for the transient temperature field prediction with interval uncertainties in both the physical parameters and initial/boundary conditions. New stability theory applicable to interval discrete schemes is developed. Interval ranges of the uncertain temperature field can be approximately yielded by two kinds of parameter perturbation methods. Different order Neumann series are adopted to approximate the interval matrix inverse. By comparing the results with traditional Monte Carlo simulation, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed model and methods. 展开更多
关键词 finite volume method temperature field prediction interval uncertainties stability theory parameter perturbationmethod
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部