共查询到20条相似文献，搜索用时 140 毫秒
1.
The growth and evolution of the knowledge network in supply chain can be characterized by dynamic growth clustering and non-homogeneous degree distribution.The networks with the above characteristics are also known as scale-free networks.In this paper,the knowledge network model in supply chain is established,in which the preferential attachment mechanism based on the node strength is adopted to simulate the growth and evolution of the network.The nodes in the network have a certain preference in the choice of a knowledge partner.On the basis of the network model,the robustness of the three network models based on different preferential attachment strategies is investigated.The robustness is also referred to as tolerances when the nodes are subjected to random destruction and malicious damage.The simulation results of this study show that the improved network has higher connectivity and stability. 相似文献
2.
In this paper,a dynamic model on a rigid rotor-sliding bearing system with a SFD is established.The stability and bifurcation behaviors of the system are studied,on The basis of the differential equations of fluid momentum and mass continuity,the distribution pressure function is derived by taking oil film inertia force into consideration.Damping force, clearance excitation force,interference force of different frequencies and static load are also considered in the model,Finally,the governing equations of the stability and bifurcation behaviors of the system are solved by Floquet theory,Simulation of dynamic model shows that the rigid rotor-sliding bearing system can maintain stability and exhibit a Hopt bifurcation phenomenon in a certain range. 相似文献
3.
Huang LF Hua XT Lu HM Gao GJ Tian B Shen BH Hua YJ 《Journal of Zhejiang University. Science. B》2006,7(5):373-376
RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement： a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose function, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ （DRRecQ） to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal （HRDC） domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism. 相似文献
4.
To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output (BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method. 相似文献
5.
Atmospheric carbon dioxide concentration [CO2], incoming solar radiation and sea ice coverage are among the most important factors that control the global climate. By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model, effects of these factors on the stability of the climatic system are studied. The current climatic system is found to be stable but highly nonlinear. The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level, suggesting carbon dioxide is essential to the stability of the global climate. With [CO2] rising further, the global climate stability decreases, the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region. When the incoming solar radiation is intensified, the ice coverage gradually diminishes, but the mean ocean temperature remains relatively constant. Overall, our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient. However, there exists a possibility of extreme states of climate, such as a snow-ball earth and an ice-free earth. 相似文献
6.
Least squares support vector machines （LS-SVMs） are modified support vector machines （SVMs） that involve equality constraints and work with a least squares cost function, which simplifies the optimization procedure. In this paper, a novel training algorithm based on total least squares （TLS） for an LS-SVM is presented and applied to multifunctional sensor signal reconstruction. For three different nonlinearities of a multifunctional sensor model, the reconstruction accuracies of input signals are 0.00136%, 0.03184% and 0.504 80%, respectively. The experimental results demonstrate the higher reliability and accuracy of the proposed method for multifunctional sensor signal reconstruction than the original LS-SVM training algorithm, and verify the feasibility and stability of the proposed method. 相似文献
7.
To facilitate stability analysis of discrete-time bidirectional associative memory (BAM) neural networks, they were converted into novel neural network models, termed standard neural network models (SNNMs), which interconnect linear dynamic systems and bounded static nonlinear operators. By combining a number of different Lyapunov functionals with S-procedure, some useful criteria of global asymptotic stability and global exponential stability of the equilibrium points of SNNMs were derived. These stability conditions were formulated as linear matrix inequalities (LMIs). So global stability of the discrete-time BAM neural networks could be analyzed by using the stability results of the SNNMs. Compared to the existing stability analysis methods, the proposed approach is easy to implement, less conservative, and is applicable to other recurrent neural networks. 相似文献
8.
田枫 《中学数学教学参考》2006,(1):119-119
Bob, Fred, and Vi play a game in which a card numbered 2,3,4,5,6,7,or 8 is stuck to each of their foreheads. Each player can see the other two players＇ numbers but not his or her own. An observ er tells the three players that the three numbers are not all different and that their product is a perfect square（安全平方数）, how many of them can deduce the number on their foreheads？ 相似文献
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10.
This paper explores the relationship between the original and its translation by interpreting Benjamin’s three metaphors from his The Translator’s Task. The exploration starts with the metaphor of“the tangent of a circle”,where it is interpreted that although the translated version should be faithful to its original in terms of meaning,yet it is a deviation due to different internal and external factors. Then,in the metaphor of“afterlife”,the discussion demonstrates that the translated version proceeds from the original,but the original depends on it for its survival and afterlife in different eras. Later,based on the metaphor of“fragments of a vessel”,the author states that the original and its translation are equal and complementary,just like the fragments of a vessel,responsible for the development and renewal of each other through translation. Finally,it is concluded that a better understanding of their relationship can offer us a new perspective in translation studies and practice. 相似文献
11.
文双春 《衡阳师范学院学报》2002,23(3):20-27
导出了非旁轴矢量传输方程，该方程明确了各修正项的物理意义；首次用变分法得到了任意初始条件下光束非旁轴传输的解析形式规律，与数值结果符合甚好。此外，基于得到的非旁轴矢量传输方程，用调制理论研究了非旁轴和矢量效应对光束自聚焦的影响，比较了各种效应的重要性，发现在自聚焦点附近，矢量效应的作用要强于非旁轴，其中矢量效应中来自电场散度项的非线性衍射的作用是最主要的。 相似文献
12.
基于瑞利衍射积分公式,推导出非傍轴离轴高斯光束相干合成和非相干合成在自由空间中传输的解析公式,用所得结果对非傍轴高斯光束相干合成和非相干合成进行了研究,得到了非傍轴公式在傍轴条件下回归到傍轴理论所得结果．远场近似,轴上光强以及傍轴离轴高斯光束的相干合成与非相干合成光束传输公式可做为本文结果的特例给出．数值计算表明,合成光束的光强分布与合成方式（相干合成和非相干合成）、光束束宽w0（或等效于f参数）、光束束数M、离轴参数α以及传输距离z有关．在远场,对于相干合成光束,M束非傍轴高斯光束的合成光束的轴上光强是单束非傍轴高斯光束的轴上光强的M^2倍;对于非相干合成光束,M束非傍轴高斯光束的合成光束的轴上光强是单束非傍轴高斯光束的轴上光强的M倍。 相似文献
13.
刘宝盈 《商洛师范专科学校学报》2013,(4):31-33
按照电磁场角动量的一般定义,研究了非近轴柱矢量光束的角动量,发现其自旋角动量主要取决于光束的偏振情况,而轨道角动量不仅取决于光束的波前相位因子,还与光束的偏振情况相关,并且都与光束的结构有关。即使在近轴近似下。柱矢量光束的角动量也不能自然地分解为互不相关的自旋角动量和轨道角动量两部分。 相似文献
14.
考虑一个受扰动的经典氢原子系统,用直接微扰法求出了该系统微扰解的一般形式,并利用Ｌｙａｐｕｎｏｖ 稳定性定理对其解的稳定性进行了分析,得到了在不同微扰下系统是Ｌｙａｐｕｎｏｖ 稳定的、渐近稳定的和不稳定的三种结局 相似文献
15.
基于小干扰稳定的概念和分析方法,通过3种不同类型的风电机组,采用PSAT软件中的特征值分析方法,研究风电机组在类型不同、风电场接入距离不同以及风电渗透率不同情况下接入WSCC 3机9节点系统时对小干扰稳定性的影响。研究结果表明:风电机组类型、接入距离以及风电渗透率均会对系统产生不同程度的影响。DFIG的影响优于另外两个机组,在风电机组确定的情况下,距离越近、风电渗透率越低对系统的小干扰稳定性越有利。 相似文献
16.
For assessments that use different forms in different administrations, equating methods are applied to ensure comparability of scores over time. Ideally, a score scale is well maintained throughout the life of a testing program. In reality, instability of a score scale can result from a variety of causes, some are expected while others may be unforeseen. The situation is more challenging for assessments that assemble many different forms and deliver frequent administrations per year. Harmonic regression, a seasonal‐adjustment method, has been found useful in achieving the goal of differentiating between possible known sources of variability and unknown sources so as to study score stability for such assessments. As an extension, this paper presents a family of three approaches that incorporate examinees' demographic data into harmonic regression in different ways. A generic evaluation method based on jackknifing is developed to compare the approaches within the family. The three approaches are compared using real data from an international language assessment. Results suggest that all approaches perform similarly and are effective in meeting the goal. The paper also discusses the properties and limitations of the three approaches, along with inferences about score (in)stability based on the harmonic regression results. 相似文献
17.
传统的高校教师的职业角色覆盖教学、科研和社会服务三大领域。若将高校作为一个学术职业系统,并沿用评价的研究范式,通过能力、同质或异质性、稳定性、集中性、一致性和动荡性六个分析维度作为比较基准,根据7所高校调研实测数据完成对现行高校学术职业从业者职业角色扮演现状的评价。研究发现,不同类型的高校对教师扮演的三大职业角色有所侧重;教书育人角色是高校教师公认的高稳定性角色,科学研究角色扮演角色呈现递增的趋势,社会服务角色存在相对稳定性。 相似文献
18.
黄瑞 《兰州石化职业技术学院学报》2014,(3):28-31
土体性质表现出其具有固有的应变特性,土体每一点的参数都会发生变化,故在边坡稳定的可靠度分析中不能被忽略。在边坡稳定分析中,常用的模拟土体随机场的模型有折减法、中点法和局部平均离散法。针对一个典型边坡,应用了三个随机场模型导出该边坡的稳定分析结果,对不同随机场模型方法得到的可靠度分析结果进行了互相对比。结果表明边坡的可靠度结果受到土体特性空间变异性的影响,并且这个影响取决于相关距离的相对尺寸和临界滑裂面长度的影响。 相似文献
19.
针对负荷波动情况,分析3种常见风电机组的结构特点;利用MATLAB的电力系统分析工具箱PSAT建立了含风电场的14节点算例系统,通过时域仿真研究了相同节点接入不同风电机组对电力系统电压稳定性的影响,对3种机组及其系统的暂态电压稳定性进行了分析对比;讨论了负荷增长方式的不同、风机接入方式的不同对风电并网点电压稳定性的影响。结果表明:负荷增长倍数越大、负荷同时增长、风机分散接入加剧了系统电压的不稳定。 相似文献
20.
阎永胜 《辽宁师范大学学报(社会科学版)》2011,34(4):105-108
语言的文化联想有三个显著特征：其一,语言所指一定是为大多数人所知道的,能够产生联想;其二,是它具有个人差别,不同生活群体或不同年龄层次的人可能对文化内涵的看法不一致;其三,是它的稳固性和可变性。历史越悠久的东西,越是稳固。一句话的含义不仅仅是几个词的意义的简单相加,有时也包含言外之意。即便是一个单词,在一定的语境或文化背景下,也可能显出言外之意。同时,也应注意到言外之意的形成因素很多,在学习语言的时候,不可忽略在不同语言环境下的联想差异。 相似文献