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1.
肌肉收缩的分子机制是什么?从量子理论出发,建立起Davydov方程组,得到孤子解,从而在微观上定量地解释了肌肉收缩,这就是Davydov孤子理论,该理论近期内又有较大发展,从孤子角度探讨某些生物问题是一条可行的途径。本文评述了Davydov孤子理论,并就该理论进行了有益的讨论。  相似文献   

2.
在忽略扩散效应的条件下,研究了温度对光折变低振幅屏蔽光伏空间暗孤子演化特性的影响.将低振幅的暗孤子解作为入射孤子波,采用数值方法求解波传播方程.结果表明,当温度一定时,晶体中可形成稳定的屏蔽光伏暗孤子,当温度变化较小时,孤子能克服小的微扰而保持其稳定性.当温度变化足够大时,孤子将变得不稳定或者崩溃.通过适当调节温度,可以控制暗孤子的空间形态.  相似文献   

3.
利用virial理论和数值模拟对色散管理光通信系统中的孤子传输进行了研究.结果表明,在普通光纤与色散补偿光纤的交界处,孤子幅度不连续,其幅度有所降低,但其形状保持不变.在小损耗光纤中传输的孤子,通过放大器幅度得到放大的同时,形状将自动得到恢复,可以稳定地、长距离不变形地传输,具有理想信息载体的特性.  相似文献   

4.
从非线性薛定谔方程出发,通过数值模拟对暗孤子在非均匀光纤系统中的稳定传输特性进行了研究。分析暗孤子传输的稳定性和孤波间的相互作用,这将为研究实际非均匀光纤或孤子控制系统中光脉冲的稳定传输和增大光孤子通信系统的容量、提供通信速率提供理论依据。  相似文献   

5.
本文在忽略扩散效应的条件下,理论研究了加偏压非光伏光折变晶体中低振幅屏蔽孤子的温度特性。结果表明,当温度一定时,晶体中可形成稳态屏蔽明孤子或暗孤子。通过适当调节温度,可以控制孤子的空间形态。  相似文献   

6.
基于小光强条件下中心对称光折变材料中空间孤子的解析结果,结合光折变材料中暗辐射强度温度特性表达式,数值分析了这种空间明孤子的温度特性,结果表明,当温度改变时,孤子的包络强度和宽度将发生变化。调控温度是改变孤子空间形态的重要手段之一。  相似文献   

7.
基于低振幅条件下中心对称光折变材料中空间孤子的解析结果,结合光折变材料中暗辐射随温度变化表达式,数值分析了这种空间孤子的温度特性。结果表明当温度升高时,孤子的强度包络变大,宽度变窄;当温度降低时,孤子的强度包络变小,宽度变宽。调控温度是改变孤子空间形态的重要手段之一。  相似文献   

8.
在忽略扩散效应的条件下,理论研究了光伏光折变晶体中低振幅屏蔽光伏暗孤子的温度特性。当温度一定时,晶体中可形成稳态屏蔽光伏暗孤子。当温度改变时,孤子由一稳态变为另一稳态。  相似文献   

9.
为了得到中心对称单光子光折变晶体中空间灰孤子族的结果,基于中心对称光折变晶体中空间灰孤子的基本理论,推出了中心对称光折变晶体中灰空间孤子数值积分解,对孤子的特性进行了数值模拟。结果表明:这些空间灰孤子族是由偏振方向和波长都相同且互不相干多数光束耦合形成的。当灰孤子族中仅含有一个或两个分量成分,它就变成单光子灰孤子或非相干耦合灰-灰孤子对。  相似文献   

10.
用Landau相交理论讨论了蛋白质孤子的热稳定性问题,进而导出了蛋白质孤子生存的临界温度Tsc.并与《科学通报》1993年第11期第1040页的论文作了对比讨论.  相似文献   

11.

Recent scholarship around teaching elementary mathematics supports the learning of early algebra with 5- to 12-year olds. However, in spite of the recognition of the affordances of early algebra, issues about how to introduce it remain open. Within this context, Davydov’s work is often cited as a source of impressive demonstration of young learners’ capacity for algebraic thinking. This work requires further exploration in order to yield a clearer picture of a very particular teaching approach, which focuses on early abstractions and symbolic language. We argue that in order to fully understand how Davydov’s work contributes to current conversations and what Davydov was trying to do, we need to shed light on the context- and time-specific discourse of the 1960 Soviet educational reforms that made it possible for Davydov to develop his vision about algebraic thinking and to set in motion appropriate teaching approaches for young learners. In this paper, we look back to the Soviet debates that unfolded in Russia on the integration of early algebra in elementary school word-problem solving. Drawing on these debates and the results of Davydov’s school experiments, we lay out the developmental axes of capacity building. This can be done by emphasizing ascent from the abstract to the concrete using a variety of representational modeling tools to support the emergence of algebraic thinking while targeting particular habits of mind within carefully designed learning activities. We conclude with some insights about current arithmetic-algebra debates, and how these could be enriched and deepened by Davydov’s work, which yet remains open to future discussion and reflection.

  相似文献   

12.
应用变分法研究了1+2维sech型光束在含有小损耗且具有e指数响应的弱非局域非线性介质中的传输特性,得到了光束各参量的演化方程、演化规律和一个临界功率.在介质损耗足够小的前提下,当光束初始功率等于临界功率时,得到了一个除了产生相移外,束宽大小可近似保持不变的1+2维sech型损耗空间光孤子.  相似文献   

13.
选取一些孤子参数的特殊值作为初始条件.利用数值解法获得了奇特的二维孤子群。进一步发现,在具有高斯响应的非线性非局域介质中,存在不同形状的高阶空间孤子群,如不对称半环状孤子、不对称项链状孤子和齿轮状孤子。这些孤子的结构,可以通过选取孤子参数的方式得到控制。  相似文献   

14.
利用改进的双曲函数法,研究离散的非线性薛定谔方程,不仅得到了离散暗孤子解,还获得了离散亮孤子解以及其它一些新形式的离散类孤子解。这种方法也同样适用于求解其它离散的非线性波方程。  相似文献   

15.

In this paper, we share details of a South African early grades’ number intervention informed by aspects of Davydov’s writing on early number teaching and learning. A key part of Davydov’s approach to early number teaching involves starting with attention to relationships between quantities rather than with counting. The Structuring Number Starters (SNS) intervention focused—over a nine-year period—on supporting early grades’ students to move beyond the calculating-by-counting approaches that are prevalent in South Africa. In attending to this focus, the intervention shifted increasingly towards an emphasis on relationships between quantities, though not in the same format or task sequence as advocated by Davydov. The contextual and cultural features that led to our adaptations—or shape-shifting—are highlighted in this paper. We interrogate key aspects of Davydov’s approaches to early number teaching in relation to key features typical of South African classroom mathematics teaching in order to understand the evolution of the SNS initiative. Quasi-longitudinal interview-based assessment data available from a cross-attainment sample of students in 2011, 2014 and 2018 indicate shifts over time from calculating-by-counting to calculating-by-structuring. These outcomes point to successes with moves into increasingly structured ways of working with early number, but suggest also that these successes may be contingent on some fluency with forward and backward number word sequences. The outcomes suggest that it is feasible to explore interventions directing attention to early number structure from the outset in larger scale studies.

  相似文献   

16.
利用多重尺度和准离散近似法研究了双原子链(相邻两原子质量不同,作用力常数交替变化)中的孤子激发。该模型模拟了闪锌矿结构晶格沿<111>方向的振动.考虑二次方和四次方作用势,得到了特殊波矢下定态孤子解的表达式.由于该晶格模型的弱对称性,其原子位移分布与文献中广泛研究的一维单原子、双原子和金刚石晶格有所不同.  相似文献   

17.
主要考虑一个(1+1)-雏孤子方程,介绍了有关孤子理论和Hirota方法,通过适当的变量代换,将孤子方程化为双线性导数形式的微分方程,从方程的双线性导数形式出发,用摄动法得到孤子方程的n-孤子解.  相似文献   

18.
文章研究了类氢原子势场作用下的二维非线性薛定谔方程即广义二维非线性薛定谔方程,得出其解是线性解对空间孤波解的调制结果,亦为孤波解,并称之为类氢孤子,并分析了二维类氢孤子在非线性介质中的传输特性。  相似文献   

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