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101.
用连续分级提取和反复多次酸提取方法研究了长期土壤酸化对红壤固相铝库中铝含量及亏损程度的影响。研究结果表明:嵊县红壤的活性铝库大于永春红壤和屯溪红壤;因永春红壤和屯溪红壤的酸化程度大于嵊县红壤,前两者的有机铝库和无机铝库都比嵊县红壤的亏损,因此反复酸提取过程中铝的释放量也比嵊县红壤少;当高强度酸输入土壤后,弱键合的有机络合态铝可快速活化并亏损,剩余铝库因活性小而释放速率减小,但长期酸化过程中,动力学控制的低活性铝库的活化可能对铝的溶解量仍有重要贡献。  相似文献   
102.
Education-driven research in CAD   总被引:1,自引:0,他引:1  
Jarek   《Computer aided design》2004,36(14):1461-1469
We argue for a new research category, named education-driven research (EDR), which fills the gap between traditional field-specific research that is not concerned with educational objectives and research in education that focuses on fundamental teaching and learning principles and possibly on their customization to broad areas (such as mathematics or physics), but not to specific disciplines (such as CAD). The objective of EDR is to simplify the formulation of the underlying theoretical foundations and of specific tools and solutions in a specialized domain, so as to make them easy to understand and internalize. As such, EDR is a difficult and genuine research activity, which requires a deep understanding of the specific field and can rarely be carried out by generalists with primary expertise in broad education principles. We illustrate the concept of EDR with three examples in CAD: (1) the Split and Tweak subdivisions of a polygon and its use for generating curves, surfaces, and animations; (2) the construction of a topological partition of a plane induced by an arbitrary arrangement of edges; and (3) a romantic definition of the minimal and Hausdorff distances. These examples demonstrate the value of using analogies, of introducing evocative terminology, and of synthesizing the simplest fundamental building blocks. The intuitive understanding provided by EDR enables the students (and even the instructor) to better appreciate the limitations of a particular solution and to explore alternatives. In particular, in these examples, EDR has allowed the author to: (1) reduce the cost of evaluating a cubic B-spline curve; (2) develop a new subdivision curve that is better approximated by its control polygon than either a cubic B-spline or an interpolating 4-point subdivision curve; (3) discover how a circuit inclusion tree may be used for identifying the faces in an arrangement; and (4) rectify a common misconception about the computation of the Hausdorff error between triangle meshes. We invite the scientific community to encourage the development of EDR by publishing its results as genuine research contributions in peer-reviewed professional journals.  相似文献   
103.
The main difficulty with EM algorithm for mixture model concerns the number of components, say g. This is the question of model selection, and the EM algorithm itself could not estimate g. On the contrary, the algorithm requires g to be specified before the remaining parameters can be estimated. To solve this problem, a new algorithm, which is called stepwise split-and-merge EM (SSMEM) algorithm, is proposed. The SSMEM algorithm alternately splits and merges components, estimating g and other parameters of components simultaneously. Also, two novel criteria are introduced to efficiently select the components for split or merge. Experimental results on simulated and real data demonstrate the effectivity of the proposed algorithm.  相似文献   
104.
于洪坤 《有色矿冶》2004,20(3):38-39
介绍了用自然澄清法降低、回收旋涡炉渣中的铜的方法。该方法工艺简单。操作方便,不仅降低冶炼成本,同时提高了经济效益。  相似文献   
105.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3.  相似文献   
106.
李海琴  张武寿 《稀有金属》2004,28(2):383-386
讨论了直流法在线测量钯氢化物电极电阻时的电化学效应,计算了电解液的共导、测量电流与电解电流引起的浓差电池效应以及电极作为集流体引起的电阻贡献。结果表明:当电极具有高的长度与半径比值、粗糙的表面、高的溶液电导以及大的电解电流时容易引起显著的附加电阻。  相似文献   
107.
Presents the 2003 American Psychological Foundation's Gold Medal Award for Life Achievement in the Science of Psychology, which was presented to Robert Rosenthal. A biography of Rosenthal is provided, along with a selected bibliography and the text of the award citation: "For outstanding scientific contributions that have had a profound influence on research methods, empirical investigations, theory, and applications. Robert Rosenthal's seminal research on interpersonal expectancy inspired hundreds of studies with applications within and beyond psychology. His amplification of experimenter- and subject-related artifacts and his insights about ethical issues have improved the way that research is conducted. His statistical contributions are classic and wide ranging, including his body of work on meta-analysis and contrast analysis and his formulation of valuable procedures, such as the binomial effect-size display and counternull statistics. An exceptional scientist, teacher, mentor, and author, Rosenthal, with his generous and brilliant touch, has shaped the lives and work of countless others." (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
108.
Using boundary element based three dimensional modelling for linear fracture mechanics, we present an analysis of cracking in a homogeneous medium subject to contact load. The proposed iterative solution procedure allows a simultaneous treatment of a reasonable number of partially closed cracks. It is shown that the most probable direction of propagation of a vertical internal crack is strongly dependent on its size compared to the contact radius and its location with respect to the axis of maximum normal load.  相似文献   
109.
The principle of maximum informational entropy is used to find the probability density function for the departure radius of a bubble in boiling on a solid surface. A general relation is derived, which leads to particular expressions.  相似文献   
110.
The paper gives the results of experimental investigations of the initial pressure gradient of bituminous oil and the time dependences of variation of the temperature in a formation model and of the well production rate in a microwave-frequency electromagnetic field. The effect of strong decay of the non-Newtonian properties of bituminous oil is revealed. The nonuniformity of temperature distribution over the formation thickness is demonstrated, which depends on the initial production rate of the well and on the duration of stimulation of the bottom-hole zone of formation.  相似文献   
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