A minimum-domain impulse theory for unsteady aerodynamic force with discrete wake

We extend the impulse theory for unsteady aerodynamics, from its classic global form to finite-domain formulation, then to a minimum-domain version for discrete wake. Each extension has been confirmed numerically. The minimum-domain theory indicates that the numerical finding of Li and Lu（2012） is of general significance： The entire force is completely determined by only the time rate of impulse of those vortical structures still connecting to the body, along with the Lamb-vector integral thereof that captures the contribution of all the rest disconnected vortical structures.

Mechanism of Gravity Impulse

It is well known that energy-momentum is the source of gravitational field. For a long time, it is generally believed that only stars with huge masses can generate strong gravitational field. Based on the unified theory of gravitational interactions and electromagnetic interactions, a new mechanism of the generation of gravitational field is studied. According to this mechanism, in some special conditions, electromagnetic energy can be directly converted into gravitational energy, and strong gravitational field can be generated without massive stars. Gravity impulse found in experiments is generated by this mechanism.

直播购物情境下用户贡献行为影响因素研究

直播购物如何促进用户作出贡献行为是直播购物发展的关键。基于SOR理论,构建直播购物情境下用户贡献行为影响模型。研究发现,信息质量、品牌形象、主播专业性与直播互动性对感知愉悦与感知信任有正向影响;感知愉悦与感知信任对消费者冲动性消费与营销信息分享有正向影响;刺激环节的变量均通过感知愉悦与感知信任对消费者冲动性消费与营销信息分享的贡献行为产生正向影响;信息质量、品牌形象不能直接对冲动性消费产生影响,且品牌形象直接对消费者的营销信息分享产生正向影响;主播专业性、直播互动性不能直接对营销信息分享产生影响,对消费者的冲动性消费产生负向影响。

信号与系统课程“翻转+智慧”课堂教学方法研究

面向新工科建设,将翻转课堂教学方法与智慧教室相结合,针对信号与系统课程,开展“翻转+智慧”课堂教学方法研究,以卷积为例给出了教学方案设计。课程教学设计坚持“以学生为中心”,教学案例体现交叉融合特点,加强过程考核,为培养满足新兴产业技术发展需求的工程创新人才奠定基础。

Research on the Relationship Between Environmental and Economic Coupling Systems in Bohai Bay Area Based on a Vector Autoregression(VAR)Model

This study analyzed the impact of land-based contaminants and tertiary industrial structure on economic development in the selected Bohai Bay area,China.Based on panel data spanning 2011-2020,a vector autoregressive(VAR)model is used to analyze and forecast the short-run and long-run relationships between three industrial structures,pollutant discharge,and economic development.The results showed that the environmental index had a long-term cointegration relationship with the industrial structure economic index.Per capital chemical oxygen demand(PCOD)and per capita ammonia nitrogen(PNH_(3)N)had a positive impact on delta per capita GDP(dPGDP),while per capita solid waste(PSW),the secondary industry rate(SIR)and delta tertiary industry(dTIR)had a negative impact on dPGDP.The VAR model under this coupling system had stability and credibility.The impulse response results showed that the short-term effect of the coupling system on dPGDP was basically consistent with the Granger causality test results.In addition,variance decomposition was used in this study to predict the long-term impact of the coupling system in the next ten periods(i.e.,ten years).It was found that dTIR had a great impact on dPGDP,with a contribution rate as high as 74.35%in the tenth period,followed by the contribution rate of PCOD up to 3.94%,while the long-term contribution rates of PSW,SIR and PNH3N were all less than 1%.The results show that the government should support the development of the tertiary industry to maintain the vitality of economic development and prevent environmental deterioration.

服饰类盲盒产品特征、推广宣传与消费者冲动购买意愿

随着盲盒市场的迅速发展,服装企业也引入“盲盒化”的营销手段。本研究的目的是探索如何推广宣传服饰类盲盒的产品特征和品牌,影响消费者的冲动购买意愿。以SOR理论模型为依据,建立服饰类盲盒的产品特征、推广宣传与消费者冲动购买意愿之间的关系模型。利用SPSS 20.0数据分析软件进行描述性统计、信度、效度检验、因子分析和回归分析。研究结果表明:服饰类盲盒的IP特征,社交特征,刺激性推广宣传,神秘性推广宣传均正向影响消费者冲动购买意愿,感知价值,感知唤醒起中介效应,根据上述研究结论,本文从服饰盲盒产品的IP特征,社交特征,刺激性营销,神秘性营销,市场现状等方面对希望推出服饰类盲盒产品的企业和品牌提出对策与建议。

冲击电弧作用下C_(4)F_(7)N/CO_(2)气体灭弧性能仿真分析

C_(4)F_(7)N/CO_(2)混合气体是目前最有潜力替代SF 6的气体之一。为了探讨C_(4)F_(7)N/CO_(2)混合气体的灭弧能力,文中根据电弧能量平衡理论,建立电弧能量平衡方程组,获取管道内部超压随时间的变化规律。同时,基于磁流体动力学模型,使用COMSOL Multiphysics软件建立压爆气流防雷间隙灭弧结构的二维磁流体模型,在雷电流幅值为4 kA的条件下,对管道内不同比例C_(4)F_(7)N/CO_(2)混合气体在冲击电弧作用下的熄弧特性进行仿真分析。基于上述方法,结合电弧能量平衡理论,分析模型中电导率、速度以及压强的变化规律。与理论结果对比分析得出:同一工况条件下,20%C_(4)F_(7)N/80%CO_(2)的灭弧性能较优,其次为10%C_(4)F_(7)N/90%CO_(2)与5%C_(4)F_(7)N/95%CO_(2),并且熄弧时间符合气吹灭弧的要求。

Impulsive control of stochastic system under the sense of stochastic asymptotical stability

This paper studies the stochastic asymptotical stability of stochastic impulsive differential equations, and establishes a comparison theory to ensure the trivial solution＇s stochastic asymptotical stability. From the comparison theory, it can find out whether the stochastic impulsive differential system is stable just by studying the stability of a deterministic comparison system. As a general application of this theory, it controls the chaos of stochastic Lii system using impulsive control method, and numerical simulations are employed to verify the feasibility of this method.

Complex dynamics analysis of impulsively coupled Duffing oscillators with ring structure

Impulsively coupled systems are high-dimensional non-smooth systems that can exhibit rich and complex dynamics.This paper studies the complex dynamics of a non-smooth system which is unidirectionally impulsively coupled by three Duffing oscillators in a ring structure.By constructing a proper Poincare map of the non-smooth system,an analytical expression of the Jacobian matrix of Poincare map is given.Two-parameter Hopf bifurcation sets are obtained by combining the shooting method and the Runge-Kutta method.When the period is fixed and the coupling strength changes,the system undergoes stable,periodic,quasi-periodic,and hyper-chaotic solutions,etc.Floquet theory is used to study the stability of the periodic solutions of the system and their bifurcations.

Multiplicity Results for Second Order Impulsive Differential Equations via Variational Methods

In this paper we investigate a class of impulsive differential equations with Dirichlet boundary conditions. Firstly, we define new inner product of <img src="Edit_890fce38-e82b-4f36-be40-9d05e8119b88.png" width="40" height="17" alt="" /> and prove that the norm which is deduced by the inner product is equivalent to the usual norm. Secondly, we construct the lower and upper solutions of (1.1). Thirdly, we obtain the existence of a positive solution, a negative solution and a sign-changing solution by using critical point theory and variational methods. Finally, an example is presented to illustrate the application of our main result.

Existence of Periodic Solution for a Non-Autonomous Stage-Structured Predator-Prey System with Impulsive Effects

In this paper, we studied a non-autonomous predator-prey system where the prey dispersal in a two-patch environment. With the help of a continuation theorem based on coincidence degree theory, we establish sufficient conditions for the existence of positive periodic solutions. Finally, we give numerical analysis to show the effectiveness of our theoretical results.

SVM-based Filter Using Evidence Theory and Neural Network for Image Denosing

This paper presents a novel decision-based fuzzy filter? based on support vector machines and Dempster-Shafer? evidence theory for effective noise suppression and detail preservation. The proposed filter uses an SVM impulse detector to judge whether an input pixel is noisy. Sources of evidence are extracted, and then the fusion of evidence based on the evidence theory provides a feature vector that is used as the input data of the proposed SVM impulse detector. A fuzzy filtering mechanism, where the weights are constructed using a counter-propagation neural network, is employed. Experimental results shows that the proposed filter has better performance in terms of noise suppression and detail preservation.

直播带货型网红特质对消费者购买行为影响研究

基于ABC消费态度理论,将直播带货型网红个人特质分为专业性、可信性、互动性和吸引力,构建直播带货型网红特质对消费者购买行为影响的研究模型,研究网红特质对消费者冲动性购买和目的性购买的影响机理。通过网络问卷调查收集数据,运用Spss Statistics 26.0和Amos 24.0对收集到的问卷进行数据分析和假设检验。研究结果表明:消费者认知性态度在直播带货型网红的专业性、互动性和吸引力与消费者目的性购买和冲动性购买之间存在中介效应;消费者情感性态度在网红的专业性、互动性与目的性购买之间存在中介效应。

正念训练对冲动性不同要素的影响:基于双加工理论

正念是指对当下身心体验不带有评判地觉察。基于双加工理论,以正念为核心的训练对个体冲动性不同要素均具有明显干预效果。一方面,有助于降低因情感系统引发的冲动驱力:通过调整个体的奖赏评估与预期,缓和诱发冲动的压力与负性情绪反应,减弱自动化反应的联结和强度;另一方面,提升个体由认知控制系统调节的冲动控制力:增强个体的认知控制和行为抑制能力。由于冲动性驱动因素和控制因素二者加工时序的先后差异和作用方向对抗性特点,正念训练促进两类要素的积极交互影响,缩小冲动性“驱动”与“控制”力量之间的不平衡,为个体更好地回应自身反应与外界刺激提供了有利缓冲,是降低个体冲动性的有效干预手段。

权力与冲动购买:权力感与购买冲动特质对冲动购买的影响

本文通过三个研究探讨了权力感对消费者冲动购买的影响。无论是测量特质权力感(研究1)还是启动状态权力感(研究2),结果均显示低权力感个体冲动购买水平更高。在考虑了购买冲动特质与权力感共同作用后(研究3),即使对于低冲动特质者,低权力感仍能使其产生与高冲动特质者相当的冲动购买水平;而高权力感个体的购买冲动特质能显著预测其冲动购买水平。研究结果表明,低权力感会导致个体冲动购买,而高权力感会促进消费者的高购买冲动特质转化为具体的冲动购买行为。

具有Hilfer分数阶脉冲微分方程边值问题解的存在性

为了拓展边值问题的基本理论,研究一类具有有限个脉冲点的Hilfer分数阶脉冲微分方程边值问题解的存在性。首先,求出微分方程等价的积分方程;其次,定义恰当的Banach空间和范数,构造合适的算子,在非线性项满足不同条件的情况下,运用Krasnoselskii不动点定理,分别得到此类边值问题存在解的充分条件;最后,通过2个实例验证研究结果的普适性。结果表明,含有Hilfer分数阶导数的脉冲微分方程边值问题的解具有存在性。运用Krasnoselskii不动点定理能够有效解决具有Hilfer分数阶脉冲微分方程边值问题解的存在性问题,丰富了分数阶微分方程理论,为解决其他类型的脉冲分数阶微分方程边值问题提供了借鉴与参考。

基于SOR理论的消费者冲动购买意愿研究——以京东商城为例

近年来,随着我国电商行业的发展,线上购物占消费者购物的比重越来越大,购物便捷的同时也引发了消费者冲动性购买现象。巨大的销售刺激因素、碎片化的购物时间、能够随时进行购物等因素都是直接引发冲动购买的导火索。基于SOR理论模型从品牌价值感知、个人特质、价格与促销、时间压力、精美包装、意见领袖、产品品质、在线评论几方面对消费者冲动性购买展开研究,通过调查问卷方式获取实证数据,验证了理论模型及各项研究假设的合理性。研究结果有助于电商平台厘清消费者冲动购物的机理,进而提升公司的市场营销策略管理水平,为其创造更大的价值。

基于一阶zigzag理论的软芯复合夹层板冲击载荷下的动态响应分析

本文提出一种简化的用于求解软芯复合材料夹层板的一阶zigzag理论模型,该模型能精确求解外载荷作用下软芯复合材料夹层板的静态和动态响应。软芯复合材料夹层板的上下面板采用一阶剪切变形理论,芯材运用线性函数模拟横向和面内位移。模型充分考虑芯材厚度方向的应力和应变,能很好满足横向剪切应力和位移界面边界条件。基于此模型,运用Newmark法求解控制方程分析冲击载荷作用下简支软芯复合夹层板的动态响应,将提出的一阶zigzag理论模型与公开发表的文献结果进行了准确性对比验证。在验证的基础上进行了一系列的参数研究,并详细研究了各种参数对夹层板动态响应的影响。计算结果能为船用软芯复合材料夹层板提供理论设计指导。

一类具有瞬时脉冲的二阶发展方程的近似可控性

该文在Hilbert空间中研究一类具有无穷时滞和瞬时脉冲的二阶中立型发展方程的近似可控性.利用余弦族理论得到该方程mild解的表示,并结合Schauder不动点定理得到mild解的存在性结论.通过构造一个适当的控制函数,并利用预解算子型条件得到该方程近似可控的充分条件.最后给出一个例子来说明主要结论的应用.

地铁工程结构破坏的竖向地震力影响分析

在 1 995年的日本阪神地震中 ,地铁工程结构发生前所未有的破坏 ,其中柱的破坏尤为严重。人们通常认为中柱的破坏是由水平地震力引起的 ,但地铁结构的有些震害现象至今无法得到圆满的解释。采用冲量理论分析竖向地震力对地铁结构中柱破坏的影响 ,能较好的解释中柱破坏的震害现象。这说明竖向地震力对地铁工程结构的破坏有显著影响。