Novel fluid inerter based tuned mass dampers for optimised structural control of base-isolated buildings

This work studies the advantageous features of the fluid inerter device for optimised structural control of buildings. Experimental data are first presented to characterise the fluid inerter dynamics, and validate the simplified analytical formulations. Building on these observations, the device is modelled as an inerter in parallel with a nonlinear dashpot representing a power law damping term. The latter dissipative effects are mainly induced by the pressure drops occurring in helical channels due to the fluid viscosity and density. Then, novel passive vibration control schemes are implemented for the earthquake protection of base-isolated buildings by combining the fluid inerter with a tuned mass damper system. To account for the uncertain nature of the earthquake input, the base acceleration is modelled as a Kanai–Tajimi filtered stationary random process. The optimal fluid inerter parameters, namely inertance and damping, are identified numerically by minimising stochastic performance indices relevant to displacement, acceleration, and energy-based measures of the structural response. The nonlinear damping behaviour of the fluid inerter is fully incorporated in the optimal design procedure via the statistical linearisation technique. Nonlinear response history analysis under an ensemble of 44 natural earthquake ground motions is carried out to assess the seismic performance of the system. Since inertance and damping are coupled characteristics in a real fluid inerter, design guidelines are finally outlined to determine the actual geometrical and mechanical properties of the device to achieve targeted parameters resulting from the optimisation procedure.     

Stability and Hopf bifurcation analysis of an eco-epidemiological model with delay

In this paper, an eco-epidemiological model with time delay is considered. The asymptotical stability of the three equilibria, the existence of stability switches about both the disease-free planar equilibrium and the positive equilibrium are investigated. It is found that Hopf bifurcation occurs when the delay τ passes through a critical value. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations at the positive equilibrium are obtained by using the normal form theory and center manifold theory. Some numerical simulations for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given.     

为π演算建立具有安全级别的简单类型系统

为π演算建立具有安全级别的简单类型系统,并证明该类型系统在规约语义下的类型可靠性.此类型系统使得π演算成为安全系统、安全协议分析与规范的普适形式化工具.     

双边道德风险情况下考虑客户知识依赖的服务合作生产契约

企业间知识密集型服务合作生产由于存在相互知识依赖,导致双方的粘性信息不能被无成本证实和监督,从而产生双边道德风险。基于客户合作视角,建立委托代理模型,从固定支付和剩余激励支付两方面分析了双边道德风险情况下客户知识依赖对服务合作生产契约设计的影响。结论表明,契约的剩余激励支付与客户知识依赖弹性系数负相关,契约的固定支付与客户知识依赖弹性系数正相关。     

Threshold behavior in a stochastic delayed SIS epidemic model with vaccination and double diseases

In this paper, we investigate the threshold dynamics of a stochastic delayed SIS epidemic model with vaccination and double diseases which make the research more difficult. We establish sufficient conditions for extinction and persistence in the mean of the two diseases. We also obtain the threshold between persistence in the mean and extinction of the stochastic system. It is shown that: (i) time delay and environmental white noise have important effects on the persistence and extinction of the two diseases; (ii) the two diseases can coexist under certain conditions. Finally, some numerical simulations are provided to demonstrate the analytical results.     

Complex dynamics and stability analysis in a discrete hybrid bioeconomic system with double time delays

In this paper, a discrete hybrid three-species food chain system is proposed, where commercial harvesting on top predator is considered. Two time delays are introduced to represent gestation delay for prey and predator population, respectively. In absence of time delay, sufficient conditions associated with economic interest and step size are derived to show system undergoes flip bifurcation. In presence of double time delays, existence of Neimark–Sacker bifurcation and local stability switch are discussed due to variations of time delays. Furthermore, by utilizing new normal form of delayed discrete hybrid system and center manifold theorem, direction and stability of Neimark–Sacker bifurcation are studied. Numerical simulations are performed not only to validate theoretical analysis, but also exhibit cascades of period-doubling bifurcation, chaotic behavior and stable closed invariant curve.     

Simple inequalities in the vibrating string and heat conduction problems

Certain inequalities are presented, related to the L² norms of the solutions to the vibrating string and heat conduction partial differential equations; in particular, an “L² maximum principle” is derived for the heat equation, and similar inequalities for the vibrating string problem.     

试论21世纪的人才策略

本文从我国加入WTO及面向21世纪的战略思考，论述了人才的重要性，提出培养和吸引优秀拔尖人才和二次人才开发策略。     

Time-series classification with SAFE: Simple and fast segmented word embedding-based neural time series classifier

Dictionary-based classifiers are an essential group of approaches in the field of time series classification. Their distinctive characteristic is that they transform time series into segments made of symbols (words) and then classify time series using these words. Dictionary-based approaches are suitable for datasets containing time series of unequal length. The prevalence of dictionary-based methods inspired the research in this paper. We propose a new dictionary-based classifier called SAFE. The new approach transforms the raw numeric data into a symbolic representation using the Simple Symbolic Aggregate approXimation (SAX) method. We then partition the symbolic time series into a sequence of words. Then we employ the word embedding neural model known in Natural Language Processing to train the classifying mechanism. The proposed scheme was applied to classify 30 benchmark datasets and compared with a range of state-of-the-art time series classifiers. The name SAFE comes from our observation that this method is safe to use. Empirical experiments have shown that SAFE gives excellent results: it is always in the top 5%–10% when we rank the classification accuracy of state-of-the-art algorithms for various datasets. Our method ranks third in the list of state-of-the-art dictionary-based approaches (after the WEASEL and BOSS methods).     

两种气溶胶质量重建方法的比较及气溶胶质量闭合研究

本文通过在WMO GAW 区域大气本底污染监测站－临安大气本底污染监测站采集的气溶胶样品的化学成分的分析结果，分别用Malm（1994）和Stelson（1981）提出的方法（分别记为Malm方法和Stelson方法）重建气溶胶质量浓度，并与称重获得的质量浓度进行对比，发现虽然Stelson和Malm方法所考虑的物质组成及所使用的化学成分个数并不相同，其计算结果略有差异，但总的来说两种方法都能较好的反映绝大部分的气溶胶质量，在实际应用中可以根据所分析的化学成分数据情况和研究的目的采用不同的质量重建方法。     

西部地区城市化与房地产业发展思路浅析

一、西部地区城市化模式选择 1、对两种主要观点的简述与评价目前,关于西部城市化的道路选择主要存在两种观点。一是“都市带”论。这种观点认为,城市区域化,城市带的形成和发展是当今世界城市化的重要趋势,改革开放以来,在我国     

简单型检索关键词性能及检索功能

本文就加强简单检索功能的问题,重点研究了关键词性能及检索功能.对检索实践中关键词的条件优先性、关键词的条件优先性的可控性及其控制问题进行了分析探讨.     

Bifurcation and control of a planktonic ecological system with double delays by delayed feedback control

In this paper, a delayed feedback controller with the delay-dependent coefficient is introduced into a multiple delay phytoplankton-zooplankton system. For uncontrolled system, choosing delays as the bifurcation parameters, we prove that Hopf bifurcation can occur when the delays change and cross some values. Then, the delays are still chosen as the bifurcation parameters to research the dynamic behaviors of the controlled system. Under this control mechanism, the onset of Hopf bifurcation can be delayed by selecting the appropriate control parameters and the stability domain can be extended as feedback gain (the decay rate) decreases (increases), and the influence of the decay rate cannot be ignored. Furthermore, using the crossing curve methods, the stable changes of equilibrium in two delay plane can be obtained. Some numerical simulations are given to verify the correctness and validity of the delayed feedback controller in the bifurcation control.     

单摆和复摆在不同摆角情形下的特性分析

在物理课教学中,单摆和复摆是一组重要的物理概念.单摆,也称数学摆,摆的质量集中在物体(视为质关)上、摆长不变;复摆,也称物理摆,摆的大小形状任意,形状大小不可忽略.文章证明单摆和复摆在较小角度情况下,作周期性简谐振动,具有等时性,当摆角较大时,分析周期与摆角之间存在复杂关系,并分析误差情况.     

浅析企业管理中的和谐管理思想及实现途径

和谐管理是以人为中心和目的,将组织中人和物的因素有机结合,将管理中科学性与艺术性有机统一的现代管理模式,包含组织内部人与人的协调以及组织与社会环境的协调,人与人以及人与社会的辨证关系是其哲学基础.实现企业和谐管理,必须解决管理过程中的各种矛盾.     

一个计算平均土壤呼吸速率和土壤碳密度的简单模型

根据大量实测的土壤碳密度资料并结合生产力模型,得到一组直接利用气候资料来计算平均土壤呼吸速率和土壤碳密度的公式,并同实测资料进行了对比.根据此模型的模拟结果,对最近基于观测资料而得出的平均土壤呼吸速率对温度变化的响应并不显著的结论提出了质疑.利用此模型还对全球潜在的土壤碳密度分布做了模拟,计算出全球土壤碳库为1152Pg.该模型成功地模拟了土壤碳密度随降水(或湿度)状况而变化的特征.     

高职经济数学“案例与实验”教学浅试

高职教育要培养学生有较强的职业综合能力和解决实际问题的能力,而传统的教学内容和方法存在一个最主要的问题就是理论与实际联系不够紧密,对于高职数学教学来说,更是如此。为改变这种状况,采用"案例与实验"相结合的方法,通过利用计算机软件,使学生探索解决一些典型数学问题的方法,可培养学生的数学应用能力和创新思维能力。     

透明波纹瓦与拉幕式遮阳网在简易厂房上的应用

针对南方地区阳光照射时间及规律,而使用一种透明波纹瓦来达到采光的目的,从而利用自然阳光照射的原理,为室内提供较好的采光条件,以达到节约能源降低生产成本,收到了一定的效果。