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排序方式: 共有79条查询结果,搜索用时 78 毫秒
1.
Andrea Dorila Cárcamo Bahamonde Josep Maria Fortuny Aymemí Joan Vicenç Gómez i Urgellés 《International Journal of Mathematical Education in Science & Technology》2017,48(3):338-352
In this article we present a didactic proposal for teaching linear algebra based on two compatible theoretical models: emergent models and mathematical modelling. This proposal begins with a problematic situation related to the creation and use of secure passwords, which leads students toward the construction of the concepts of spanning set and span. The objective is to evaluate this didactic proposal by determining the level of match between the hypothetical learning trajectory (HLT) designed in this study with the actual learning trajectory in the second experimental cycle of an investigation design-based research more extensive. The results show a high level of match between the trajectories in more than half of the conjectures, which gives evidence that the HLT has supported, in many cases, the achievement of the learning objective, and that additionally mathematical modelling contributes to the construction of these linear algebra concepts. 相似文献
2.
本文设计开发了一种以2,6-二甲酰基对甲苯酚为母体的新型荧光探针HMI,可用于高效识别EtOH-H2O (8/2, v/v, HEPES 10 mM, pH =7.4)体系中的CO32-。HMI在660 nm处显示发射带,加入CO32-后,在600 nm的等吸收点激发时,原来在660 nm处的荧光淬灭,而以540 nm为中心的新发射带荧光显着增加,为比率型荧光探针。HMI对CO32-表现出高选择性且具有较强的抗干扰能力。此外,荧光探针HMI对CO32-荧光响应的检测限较低,可达到3.938×10-6 M。更具有意义的是,HMI探针对CO32-的检测能够在实际水样中起到很好的应用,而且细胞成像研究表明,HMI可用于活体MCF-7细胞中CO32-的成像。 相似文献
3.
舰船光电对抗中烟幕遮蔽与激光引偏的配合作战研究 总被引:1,自引:1,他引:0
通过分析舰船光电对抗作战中烟幕干扰和激光引偏干扰的特点,提出了烟幕遮蔽和激光引偏在对抗半自主激光制导武器时配合使用的作战样式,分析了各种作战样式的使用条件、工作流程和配合要素,以及作战样式的优势与不足,指出了多种干扰手段配合作战是发挥光电对抗系统综合对抗效能的关键. 相似文献
4.
5.
我们研究了4种负载型Pt催化剂(1Pt/NiO、1Pt/FeOx、1Pt/Co3O4和Pt/CeO2)上不同反应条件下CO氧化活性及抗H2O和CO2性能.发现反应气氛中CO2的加入与CO形成了竞争吸附,并在催化剂表面形成了碳酸盐物种堵塞了活性位,从而导致催化剂失活.反应气氛中H2O的加入对1Pt/CeO2催化剂的活性有所抑制,但对1Pt/FeOx、1Pt/NiO和1Pt/Co3O4催化剂的活性却有促进作用.在1Pt/FeOx和1Pt/CeO2催化剂上的分步反应实验和动力学研究表明,尽管H2O的加入在两种催化剂上均与CO形成了竞争吸附,但在1Pt/FeOx催化剂上H2O在载体表面解离形成的羟基更易与CO反应,开辟了新的反应途径,从而提高了反应性能.此外,H2O的加入能有效分解该催化剂上的碳酸盐物种,从而保持了其稳定性. 相似文献
6.
Systematic evolution of ligands by exponential enrichment is a traditional approach to select aptamer, which has a great potential in biosensing field. However, chemical modifications of DNA library or targets before selection might block the real recognition and binding sites between aptamers and their targets. In this study, a label‐ and modification‐free‐based in situ selection strategy was developed to overcome this limitation. The strategy is an attempt to screen bovine serum albumin aptamers according to the principle of electrophoretic mobility shift assay, and allowed single‐stranded DNA sequence to be fully exposed to interact with bovine serum albumin which was mixed with the agarose gel beforehand. After eight rounds of selection, specific aptamer with low dissociation constant (Kd) value of 69.44 ± 7.60 nM was selected and used for subsequent establishment of fluorescence biosensor. After optimization, the optimal aptasensor exhibited a high sensitivity toward bovine serum albumin with a limit of detection of 0.24 ng/mL (linear range from 1 to 120 ng/mL). These results indicated that the label‐ and modification‐free‐based in situ selection strategy proposed in this work could effectively select specific aptamer to develop aptasensor for sensitive detection of bovine serum albumin or other targets in actual complicated samples. 相似文献
7.
A kind of second-order implicit upwind fractional step finite difference methods are presented for the numerical simulation of coupled systems for enhanced(chemical)oil production with capillary force in the porous media.Some techniques,e.g.,the calculus of variations,the energy analysis method,the commutativity of the products of difference operators,the decomposition of high-order difference operators,and the theory of a priori estimate,are introduced.An optimal order error estimate in the l~2 norm is derived.The method is successfully used in the numerical simulation of the enhanced oil production in actual oilfields.The simulation results are satisfactory and interesting. 相似文献
8.
The paper is concerned with the problem of predicting nonlinear creep strains and time to ductile rupture of prismatic rods
under constant tension. The material of the rod is assumed isotropic, homogeneous, and perfectly plastic. The problem is solved
using models that take into account the change in the geometry of the rod during creep, the finiteness of the creep strains,
and the effect of the initial and actual elastic strains. The conditions whereby the characteristic dimension of the rod tends
to infinity and the accumulated and real strains in the viscous flow are limited are used as a failure criterion. The calculated
results are compared with experimental data for a number of steels and alloys to formulate the conditions for the ductile
rupture and embrittlement of metallic materials under uniaxial creep
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Translated from Prikladnaya Mekhanika, Vol. 44, No. 4, pp. 120–133, April 2008. 相似文献
9.
舰艇对抗微分对策建模研究 总被引:1,自引:0,他引:1
编队舰艇对抗攻击瞬时运动状态过程的完整描述是一个尚未很好解决的技术难点,本就驱逐舰对多艘导弹快挺对抗攻击建模问题进行了研究,建立了攻击时间尽可能短的定量微分对策模型,并给出了具体实现方法,中模型和方法可为实时舰艇作战指挥系统的研制、开发提供技术支持及理论依据。 相似文献
10.