Performance analysis of high-static-low-dynamic stiffness vibration isolator with time-delayed displacement feedback

The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.

Static output feedback control for discrete-time fuzzy bilinear system

The problem of designing fuzzy static output feedback controller for T-S discrete-time fuzzy bilinear system （DFBS） is presented. Based on parallel distribution compensation method, some sufficient conditions are derived to guarantee the stability of the overall fuzzy system. The stabilization conditions are further formulated into linear matrix inequality （LMI） so that the desired controller can be easily obtained by using the Matlab LMI toolbox. In comparison with the existing results, the drawbacks, such as coordinate transformation, same output matrices, have been elim- inated. Finally, a simulation example shows that the approach is effective.

Experimental study on freezing of liquids under static magnetic field

Freezing processes of several liquids under static magnetic field(SMF) less than 50 mT were investigated. Central temperature of liquid samples held in glass test tubes immersed in a liquid bath was measured and collected. Nucleation temperature and phase transition time were obtained from freezing curves. Normality tests were performed for nucleation temperature of these liquids with/without magnetic field and normality distributions were justified. Analysis of variances was carried out for nucleation temperature of these liquids with magnetic field flux density as the influencing factor. Results showed that no significant difference was found for deionized water with or without SMF. However, differences exist in 0.9% NaCl solution and 5% ethylene glycol solution with and without SMF. Nucleation temperature of 0.9% NaCl with SMF is lower than that without SMF, while its phase transition time is shorter than that without SMF. Nucleation temperature of 5% ethylene glycol with SMF is higher than that without SMF, while its phase transition time is not modified with SMF.

Stability Analysis for Recurrent Neural Networks with Time-varying Delay

This paper is concerned with the stability analysis for static recurrent neural networks （RNNs） with time-varying delay. By Lyapunov functional method and linear matrix inequality technique, some new delay-dependent conditions are established to ensure the asymptotic stability of the neural network. Expressed in linear matrix inequalities （LMIs）, the proposed delay-dependent stability conditions can be checked using the recently developed algorithms. A numerical example is given to show that the obtained conditions can provide less conservative results than some existing ones.

A study on the seismic behavior of a retrofitted building based on nonlinear static and dynamic analyses

This study describes the seismic performance of an existing five storey reinforced concrete building which represents the typical properties of low-rise non-ductile buildings in Turkey. The effectiveness of shear walls and the steel bracings in retrofitting the building was examined through nonlinear static and dynamic analyses. By using the nonlinear static analysis, retrofitted buildings seismic performances under lateral seismic load were compared with each other. Moreover, the performance points and response levels of the existing and retrofitting cases were determined by way of the capacity-spectrum method described in ATC-40 (1996). For the nonlinear dynamic analysis the records were selected to represent wide ranges of duration and frequency content. Considering the change in the stiffness and the energy dissipation capacities, the performance of the existing and retrofitted buildings were evaluated in terms of story drifts and damage states. It was found that each earthquake record exhibited its own peculiarities, dictated by frequency content, duration, sequence of peaks and their amplitude. The seismic performance of retrofitted buildings resulted in lower displacements and higher energy dissipation capacity depending mainly on the properties of the ground motions and the retrofitting strategies. Moreover, severe structural damage (irreparable or collapse) was observed for the existing building. However, buildings with retrofit alternatives exhibited lower damage levels changing from no damage to irreparable damage states.

Embodiment of Tradition and Modernity:Reading the Notion of Time in One Hundred Years of Solitude and Ba Ba Ba

Compared masterpiece of the Latin American Literature--One Hundred Years of Solitude with traditional Chinese significant novel--Ba Ba Ba written by Han Shaogong,the author suggested the notion of time in One Hundred Years of Solitude and Ba Ba Ba consists of two levels of narrative:static time and dynamic time. They provide readers with different perspectives in evaluating the thematic issues of the novels.

Graph Modeling for Static Timing Analysis at Transistor Level in Nano-Scale CMOS Circuits

The development and the revolution of nanotechnology require more and effective methods to accurately estimating the timing analysis for any CMOS transistor level circuit. Many researches attempted to resolve the timing analysis, but the best method found till the moment is the Static Timing Analysis (STA). It is considered the best solution because of its accuracy and fast run time. Transistor level models are mandatory required for the best estimating methods, since these take into consideration all analysis scenarios to overcome problems of multiple-input switching, false paths and high stacks that are found in classic CMOS gates. In this paper, transistor level graph model is proposed to describe the behavior of CMOS circuits under predictive Nanotechnology SPICE parameters. This model represents the transistor in the CMOS circuit as nodes in the graph regardless of its positions in the gates to accurately estimating the timing analysis rather than inaccurate estimating which caused by the false paths at the gate level. Accurate static timing analysis is estimated using the model proposed in this paper. Building on the proposed model and the graph theory concepts, new algorithms are proposed and simulated to compute transistor timing analysis using RC model. Simulation results show the validity of the proposed graph model and its algorithms by using predictive Nano-Technology SPICE parameters for the tested technology. An important and effective extension has been achieved in this paper for a one that was published in international conference.

NanoTime在65nm高速SRAM IP设计中的应用

随着集成电路制造工艺发展到90nm以下,纳米级效应对时序的影响越来越显著。对于全定制数字电路,精确评估内部信号完整性(SI)尤为重要。高速SRAM IP采用65nm工艺全定制设计,我们选择Synopsys公司的NanoTime来分析信号完整性。本文详细介绍了NanoTime静态时序分析、SI分析、时序模型提取在SRAM IP设计中的应用。

Ultraslow Relaxation Process of Static Light Scattering Intensity by Boron Oxide above the Glass Transition Temperature

The data describing of the light scattering intensity relaxation above the glass transition temperature by boron oxide obtained by using of the temperature jump methods are presented. It is found that the stabilization of the glass at 220℃ resulted in increasing of the anisotropic intensity at the same time the isotropic intensity is not practically unchangeable. It is shown that after the temperature jump to 330℃the intensity is characterized by the formation of a maximum. This effect is in compliance with the results obtained for the other oxide glasses. It is established that characteristic time of the relaxation of the maximum height is about two orders of magnitude more than the structural relaxation time for this temperature.

黑龙江省成年人身体活动和静态行为状况分析

目的:了解黑龙江省成年人身体活动和静态行为状况并进行分析,为改善居民不良生活习惯提供参考。方法:2018年6—12月,采用多阶段随机整群抽样法,选取黑龙江省10个县(市、区)作为国家级慢性病与营养监测点,对监测点18岁及以上居民进行身体活动和静态行为问卷调查。结果:调查对象经常锻炼率为15.70%,从不锻炼率为77.70%,日平均总静态行为时间为(4.60±2.69) h,日平均看电视、使用电脑、玩电子游戏、使用手机的屏幕时间为(2.82±2.02) h,日平均睡眠时间为(7.14±1.63) h。结论:黑龙江省成年人经常锻炼率较低,身体活动不足普遍存在,业余静态行为时间较长。相关部门应关注居民身体锻炼情况,由体育指导员引领居民开展适合的体育活动;应通过提高人群的经常锻炼率和缩短屏幕时间防控慢性病;应加强健康宣传与促进,使居民意识到身体活动的益处,从而提高居民的健康水平。

GPS measured static and kinematic offsets at near and far field of the 2011 Mw 9.0 Tohoku-Oki earthquake

The Mw 9.0 Tohoku-Oki earthquake that hit the mainland Japan on 11 th March, 2011 had resulted a devastating Tsunami due to an active thrusting between the Pacific and the North American Plates. Static and kinematic offsets at the offshore epicentre of the Mw 9.0 event remain unanswered and being investigated along with their near and far field limiting distances from the epicentre. Accordingly, offset measurements from 60 continuously operating IGS and GEONET GNSS stations were radially classified from the epicentre and interpreted with analytical models to find their linear offset decay rates. Co-and post-seismic static positional anomaly offsets of sixty days show almost all near field stations had strong or appreciable eastward or south eastward static shifts. Near stations(<250 km) showed both kinematic and static offsets. GEONET station ’0175’ showed maximum resultant static offset of-4.5 m, which diminishes approximately 1-2 cm at far sites like SMST and AIRA. Characteristic decay duration(’b’) of the mean kinematic co-seismic shift(’a’)of near field stations was 17.28 s during earthquake hours with an EW component shift >1.5 m. Spatial models of projected N-S static and kinematic offsets show their asymmetrical distributions around the epicentre with maximum model offset of-1.84 m displaced towards south at-45 km north of the epicentre. The Tohoku-Oki earthquake produced a resultant kinematic offset of-10.2 m towards East at its offshore epicentre;while the estimated near field static offset is ~9.82 m. However, both estimates are bigger than double the resultant offset measured value(~4.3 m) in the Japanese mainland using GPS. The difference in the kinematic and static near field offsets highlight that the near surface had elastic or in-elastic kinematic strain dissipation as against the lithospheric level viscoelastic static response, which resulted rapid kinematic strain release(1.12 cm/km)within the limiting radius of ~220 km from the Tohoku-Oki epicentre.

Nonlinear parametrically excited vibration and active control of gear pair system with time-varying characteristic

In the present work, we investigate the nonlinear parametrically excited vibration and active control of a gear pair system involving backlash, time-varying meshing stiffness and static transmission error. Firstly, a gear pair model is established in a strongly nonlinear form, and its nonlinear vibration characteristics are systematically investigated through different approaches. Several complicated phenomena such as period doubling bifurcation, anti period doubling bifurcation and chaos can be observed under the internal parametric excitation. Then, an active compensation controller is designed to suppress the vibration, including the chaos. Finally, the effectiveness of the proposed controller is verified numerically.

准静态环境下的回溯加扰密钥生成算法

物理层安全技术利用无线信道环境动态生成密钥,但在准静态环境中,信道变换缓慢导致密钥的随机性及安全性不足,因而提出一种回溯加扰密钥生成算法(Backtracking Scrambled Key Generation,BSKG).首先,拆分信道系数的实部虚部量化以生成更长的密钥.调和后,再利用本次密钥与上一次密钥间的不一致索引总和生成扰码并与本次密钥加扰.仿真结果表明,较现有的多维信息、添加人工随机性的密钥生成方法,本文算法具有更高的密钥生成速率和安全性,且随“一次一密”密钥生成次数的增加,即使被窃听到较相关的信道系数,密钥泄露率仍接近0.5.利用语义安全和信息论不等式分别估计一般及恶劣信道条件成功窃听的概率上界及其随密钥生成次数N的变化情况,给定某些参数,得到这两种情况下的概率上界分别为2-77N和2-23N.

用于多元时间序列预测的图神经网络模型

现有用于多元时序预测的图神经网络模型大多基于预定义图以静态的方式捕捉时序特征,缺少对于系统动态适应和对时序样本之间潜在动态关系的捕捉.提出用于多元时序预测的图神经网络模型(MTSGNN).该模型在一个图学习模块中,采用数据驱动的方式学习时间序列数据的静态图和动态演化图,以捕捉时序样本之间的复杂关系.通过图交互模块实现静态图和动态图之间的信息交互,并使用卷积运算提取交互信息中的依赖关系.利用多层感知机对多元时序进行预测.实验结果表明,所提模型在6个真实的多元时间序列数据集上的预测效果显著优于当前最先进的方法,并且具有参数量较小、运算速度较快的优点.

矩形钢管混凝土束风机塔筒风振特性研究

随着风电资源优势区开发逐渐饱和,风电开发的重心开始向风资源条件相对恶劣的低风速地区转移,分布式、大功率、高塔筒和长叶片已经成为风电行业发展趋势。基于此提出了一种新型的矩形钢管混凝土束风机塔筒,该塔筒由矩形钢管混凝土束拼接而成,具有强度高、刚度大和耗能能力强的优点。为研究该塔筒结构的风振响应特性,选用Kaimal脉动风速功率谱,采用谐波合成法模拟风荷载时程曲线,对其进行了动力时程分析,并计算了风振系数及等效静力风荷载。结果表明:该新型塔筒在额定风速下位移塔顶位移最大值为911.84 mm,对应的水平位移角为1/154,符合规范要求。塔筒各构件的强度较好,且具有较大的安全富余度。基于位移等效的阵风荷载因子法计算得到的风振系数值较低;在惯性风荷载法计算得到的等效静力风荷载作用下,结构位移、基底剪力与结构随机振动分析得到的基本一致。

静停时间对长江下游蒸养疏浚砂浆特性的影响

长江下游航道疏浚产生大量疏浚砂,疏浚砂的资源化利用受到重视。利用疏浚砂部分取代机制砂制备砂浆,研究不同静停时间对疏浚砂砂浆特性的影响,测试不同龄期的抗压强度,通过X射线衍射、扫描电镜、压汞技术,分析不同静停时间、不同疏浚砂取代率砂浆的微观特性。结果表明:随着静停时间的增加,90 d抗压强度逐渐增加,抗渗性能得到明显改善;掺入疏浚砂使得砂浆的抗压强度有所提高,且随疏浚砂取代率的增加先增大后减小;疏浚砂砂浆的抗压强度与疏浚砂取代率有较大关系,其影响程度与静停时间有关,疏浚砂对低静停时间有较突出的增强效果;疏浚砂有效改善了由蒸养造成的孔结构粗化和孔隙增大等问题,适宜的疏浚砂取代率对蒸养砂浆性能的改善效果明显。

未知工艺角下时序违反的机器学习预测

集成电路设计复杂性的增长以及工艺尺寸的持续缩减给静态时序分析以及设计周期带来了新的严峻挑战。为了提升静态时序分析效率、缩短设计周期,充分考虑FinFET工艺特性以及静态时序分析原理,提出了未知工艺角下时序违反的机器学习预测方法,实现了基于部分工艺角的时序特性来预测另外一部分工艺角的时序特性的目标。基于某工业设计进行实验,结果表明,提出的方法利用5个工艺角时序预测另外31个工艺角时序,可达到小于2 ps的平均绝对误差,远远优于传统方法所需的21个工艺角,显著改善了预测精度和减少了静态时序分析工作量。

一种基于机器学习的众工艺角延迟预测方法

在不同工艺角下,关键路径呈现显著差异,因此需要进行大量的静态时序分析,从而导致时序分析运行时间较长。与此同时,随着工艺尺寸的缩小,静态时序分析的精度问题变得不容忽视。本文提出一种基于机器学习的适用于众工艺角下的延迟预测方法,考虑工艺、电压和温度对时序的影响,利用基于自注意力Transformer模型对关键路径进行全局聚合编码,预测众工艺角下关键路径的统计延迟。在EPFL基准电路下进行验证,结果表明该方法的平均绝对误差范围为5.8%~9.4%,有良好的预测性能,可以提高时序分析的准确度和效率,进而缩短数字电路设计周期和设计成本。

茫荡山杉木天然种群结构与生态位特征

【目的】了解杉木在天然林中的种群结构及其生态位特征,为杉木近自然经营提供依据。【方法】以茫荡山国家级自然保护区内有杉木分布的天然林为研究对象,设立3200 m^(2)的样地,进行样地内乔木、灌木及草本种类和数量的全面调查,绘制杉木种群径级结构,计算种群结构动态变化指数,编制静态生命表,对2、4、6、8个龄级时间后的杉木种群进行时间序列预测,计算生态位宽度及杉木与其他物种的生态位重叠指数。【结果】杉木天然种群幼苗能够正常更新,但Ⅱ、Ⅲ龄级个体数量较少。随着龄级的增加,杉木种群的个体数量先增加后减少,年龄结构呈纺锤型分布,总体呈现衰退趋势。杉木种群中死亡率为负的龄级较多,整体表现出波动趋势。杉木种群的生命期望随龄级增加呈下降趋势。经过2、4、6、8个龄级时间后,杉木种群中小龄级个体数量略微下降,大龄级个体数量略微增加。杉木种群的相对优势度、相对密度、相对频度和重要值均处于群落前列,属群落建群种。不同杉木种群的生态位宽度值较大,与其他物种的生态位重叠指数也较高,说明其对环境资源的竞争激烈。【结论】在茫荡山天然林中,杉木幼苗能够正常更新,但存活率较低。杉木对群落环境资源的利用并没有明显的优势,杉木种群总体呈衰退趋势。