规范反应谱长周期部分修正方法的探讨

为将反应谱方法应用于长周期大跨度桥梁结构的抗震设计,本文探讨了对现有公路工程抗震设计规范中地震反应谱的长周期段进行修正的方法.数字化强震记录反应谱的计算结果表明,地震动水平分量的位移反应谱可以有一个明显的峰点.同时当周期无限长时,地震动相对位移反应谱应等于地面运动位移最大值.以此为基础,增加了表达长周期地震动反应谱特性的参数.经过修正和补充的规范化反应谱可用于长周期大跨度桥梁结构的抗震设计.

基于小波变换的长周期桥梁选波方法研究

时程分析输入地震波的选取对长周期大跨度桥梁影响显著。本文基于规范目标谱,以MATLAB为依托,通过选取最优小波基并利用小波系数迭代法实现频域调整,使地震波反应谱不断逼近给定目标谱,最后结合相对误差和长周期拟合参数两个指标进行综合评价,选取适用于长周期大跨度桥梁的时程分析地震波,提出长周期桥梁全过程批量选波方法。将该方法应用于奉节长江大桥,与基于时域调整方法的Seismo Match选波软件对比选波效果,并将选波结果应用于背景桥梁的时程分析。结果表明,利用本文选波方法所得结构关键截面响应与软件选波所得响应在横桥向和竖桥向存在一定差异。本文方法可为长周期大跨度桥梁时程分析选波提供参考。

一类任意周期的周期函数

用取整函数y＝[x]构作了一类以任意正实数为周期的周期函数。

螺旋槽管管内强化传热的三维数值模拟

基于周期段模型,对不同结构参数的螺旋槽管管内流动和换热进行了三维数值模拟,得到了管内流体湍流流动的速度场和温度场的细观分布.结果表明,随着槽深增大,螺旋槽管换热性能增强的同时阻力系数也相应增大;随着螺距增大,其换热性能减弱且阻力系数明显减小.最后,结合模拟结果数据,拟合出了努赛尔数Nu和阻力系数f的相应关联式.

管壳式换热器模块综合模拟方法研究

通过对折流板管壳式换热器壳程流体流动和传热特性分析,提出了1种模块综合模拟方法.该方法将折流板管壳式换热器壳程分为进口段、周期段和出口段,并分别进行模拟计算,而后将各部分模拟结果进行综合得到整个壳程的温差和压力降.并通过管壳式换热器传热性能实验和数值模拟结果进行对比,两者吻合较好,证明了该数值模拟方法的正确性.模块综合法可以减少计算模型的网格数量,提高计算速度,而且具有较高的精确性,可以用于较大型管壳式换热器的模拟计算,弥补了传统模拟方法的不足.

可移动文物隔震系统的地震动破坏强度排序

为研究不同地震动对可移动文物的潜在破坏能力,本文以可移动文物隔震装置设计中的输入地震动为研究对象,推荐了典型周期的隔震系统输入地震动破坏强度排序.通过引入累积分布函数,并将结构根据周期划分为短、中、长3个频段,在每个周期段内建立典型隔震系统模型,基于隔震系统的非线性地震响应进行地震动破坏强度排序并合理优化,将优化后排序与基于隔震系统自振周期对应的弹性加速度反应谱值排序进行对比.结果表明:对于Ⅰ类场地,短周期模型的两种排序相似性约为75%;对于Ⅱ类场地,3个周期段模型的排序相似性高达90%以上,可以根据加速度反应谱排序定量选取输入地震动;对于Ⅲ类场地,排序相似性低于前两类场地,但对于中长周期隔震系统仍有70%的相似性.因此,基于单自由度弹性加速度反应谱排序结果,可为可移动文物隔震系统设计时选择输入不同破坏强度的地震动提供定量参考.

CALCULATING ACCURATE PERIODIC MOTIONS OF HARMONICALLY FORCED PIECEWISE LINEAR OSCILLATORS

This paper presents an efficient numerical scheme for calculating the periodic motion of a harmonically forced piecewise linear oscillator very accurately. The scheme is based on the shooting technique with the traditional numerical Poincare mapping and its Jacobian replaced by the piecewise analytic ones. Thus, the scheme gets rid of the requirement of the current schemes for an assumed order of the oscillator trajectory passing through different linear regions. The numerical examples in the paper demonstrate that the new scheme, compared with the current schemes, enables one to cope with more complicated dynamics of harmonically forced piecewise linear oscillators.

Dual-frequency whole body vibration enhances vertical jumping and change-of-direction ability in rugby players

Background:Traditional vertical and side-alternating whole body vibrations(WBV) can effectively improve muscle power performance but have a limited efficacy for enhancing change-of-direction(COD) ability.Novel dual-plate WBV uniquely providing various directions of movements with higher and distinctive frequencies for each leg may cause better acute effect on muscle power and stretch-shortening cycle efficacy contributing to COD ability.Therefore,the purpose of this study was to investigate the acute effect of dual-or single-frequency WBV on squat jumps(SJs),countermovement jumps(CMJs),eccentric utilization ratios(EURs),and COD ability in rugby players.Methods:Fourteen male rugby players were recruited and performed a 4 min partial squat with 3 types of WBV protocols on a dual-plate WBV machine,including 1 dual-frequency WBV protocol(DFW) with the dominant leg receiving 35 Hz and the non-dominant leg receiving 45 Hz,and2 single-frequency WBV protocols(SFWs) with 35 Hz or 45 Hz provided to both legs(SFW35Hz and SFW45Hz) on 3 different days.Results:The results showed that all the vibration protocols significantly improved SJ and CMJ performances(SJ:p = 0.008;CMJ:p < 0.001),but did not significantly change EURs(p > 0.05).In addition,only the DFW significantly improved COD ability(p = 0.001 for the pre–post comparison).Conclusion:A 4 min dual-frequency WBV session improved both vertical jumping and COD ability in rugby players,suggesting that this could be a potential warm-up protocol for athletes.

Effect of p27mt gene on apoptosis of the colorectal cancer cell line Lovo

AIM： To construct p27mt recombinant adenovirus, transfect the colorectal cell line Lovo and observe the effects of p27mt on Lovo cell apoptosis and cell cycle inhibition. METHODS： We constructed recombinant adenovirus containing p27mt by homologous recombination in bacteria. The colorectal cancer cell line Lovo was infected with recombinant replication-defective adenovirus Ad- p27mt, and expression of p27mt was determined by Western blotting; the inhibitory effect of p27mt on Lovo cells was detected by cytometry. Cell cycle was determined by flow cytometry. DNA fragment analysis identified the occurrence of apoptosis. RESULTS： The recombinant adenovirus which already contained p27mt target gene was successfully constructed. When multiplicity of infection was ≥50, the infection efficiency was 100%. After transfection of Lovo cells with Ad-p27mt the cells had high p27 expression which was identified by immunoblotting assay. PI staining and flow cytometry showed that 77.96% of colorectal cancer cells were inhibited in phase G0/G1, while in the Ad-LacZ group and blank control group, 27.57% and 25.29% cells were inhibited in the same phase, respectively. DNA fragment analysis, flow cytometry and TUNEL assay demonstrated that p27mt is able to induce apoptosis in colorectal cancer cells. CONCLUSION： p27mt has an obvious blocking effect on colorectal cancer cell cycle, and most cells were inhibited in phase G0/G1. Therefore, p27mt can induce apoptosis in colorectal cells.

分段双加权伪概周期函数及其分解唯一性

介绍了分段双加权伪概周期函数的概念.分段双加权伪概周期函数可以看做是分段加权伪概周期函数的推广也可以认为是双加权伪概周期函数的推广.首先给出分段双加权伪概周期函数的概念,然后介绍几个分段双加权伪概周期函数的几个性质:分解唯一性,分段双加权遍历空间的平移不变性.

高烈度地区超高层结构的强震记录选取方法研究

针对一幢位于高烈度地区的超高层结构进行了罕遇地震情况的地震波选取,通过弹塑性时程分析对比了控制周期延长段加速度谱偏差的方法与目前常用的控制主要周期处反应谱偏差的方法的选波效果。控制周期延长段反应谱偏差的方法反映了结构的弹塑性发展,理论上更适用于高烈度地区超高层结构在罕遇地震情况下的地震波选取。时程分析结果也表明,控制周期延长段反应谱偏差的方法较好的控制了结构非线性地震响应的离散性。

Signal timing optimization model based on dual-ring phase scheme for roundabout

A signal optimization model for roundabout was control concept were used to eliminate the conflict points proposed based on dual-ring scheme and two stop lines for left turns and weaving sections at a roundabout. A cycle length minimization problem was considered to generate optimal signal timings for roundabout, and a set of constraints to ensure feasibility and safety of the resulting optimal signal settings were proposed. Extensive experimental analyses in comparison with signalized intersection reveal that the proposed model is quite promising for application in design of roundabout signals, and the minimum cycle length can decrease from 186 s to 79 s while the capacity increases from 8 682 pcu/h to 9 011 pcu/h under high demand scenario. Sensitivity analysis with respect to the system performance show that the lane assignment plan, number of circulatory lanes and left turn ratio are three critical factors which have dominate impacts on performance of signalized roundabout

Debt Rating Initiations： Natural Evolution or Opportunistic Behavior？

The authors examine a firm＇s decision to begin issuing debt in public bond markets and find that it is a function of both life cycle influences and opportunistic timing. Defining life cycle factors to encompass both a firm＇s age in years and its underlying characteristics, the authors confirm that bond market participation is generally restricted to large, mature firms. Summary statistics show that finns obtain their initial bond ratings on average 9.5 years after their equity initial public offering （IPO） and 11.8 years after initiating dividend payments. Growth rates, capital expenditures, and cash flow volatility all decline as the firm accesses public debt markets, consistent with entry into the mature phase of its life cycle. With respect to opportunistic timing, it is asked whether entry into public bond markets follows strong performance （or precedes weak performance） at both the firm and market levels. At the firm level, the authors find that the debt IPO occurs following periods of strong operating performance and high excess stock returns. At the market level, entry coincides with favorable interest rates and default spreads. The benefits of careful timing result in firms receiving initial bond ratings that are stronger than what would be predicted; however, there is no evidence of abnormal numbers of downgrades for these firms in subsequent years.

Evaluation of Environmental Impacts of Traction Motor Production and Disposal

By the application of life cycle assessment(LCA) methodology, this paper estimates the environmental impacts of production and disposal of traction motors used in electric vehicles in China. The results show that the total energy use, the criteria emissions and the greenhouse gases(GHG) emissions of a traction motor production and disposal are about 2,899,MJ, 4.5,kg and 259.5,kg per motor, respectively. Among the regulated emissions, the SOxemission ranks first by total mass, followed by CO, PM10, NOx, PM2.5, and volatile organic compound(VOC). The motor material production stage accounts for most of the energy consumption and emissions, followed by the assembly stage and the end-of-life disposal stage. In this study, the environmental performance analysis is extended to the comparison between the use of secondary material and primary material for the material production stage. It is found that using 100% secondary material results in a 52.9% reduction in energy consumption, a 49.8% reduction in regulated emissions, and a 49.3% reduction in GHG emissions compared with the use of 100% primary material.

Gravitational Waves from a Pseudo-Newtonian Kerr Field with Halos

A close relation between gravitational waveforms and the types of trajectories in a superposed field between a pseudo-Newtonian Kerr black hole and quadrupolar halos is shown in detail The gravitational waveforms emitted from circular, KAM tori and chaotic orbits must be periodic, quasiperiodic and stochastic, respectively. The chaotic motion can maximally enhance both the amplitudes and the energy emission rates of the waves.

Experimental study on pressure fluctuation characteristics of slug flow in horizontal curved tubes

In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference and 26 mm inner diameter are used. When the superficial liquid velocity or the superficial gas velocity is constant,the pressure fluctuations and the probability distribution of the average velocity of slug flow are clear for all of the five experimental conditions. The results of experiment show that the pressure characteristics of slug flow in curved tubes have periodic fluctuations. With the rise of central angle,the period of pressure fluctuation is more obvious. The system pressure of the slug flow increases with the increasing of superficial liquid/gas velocity. Meanwhile,the probability distribution of pressure signal shows regularity,such as unimodal,bimodal or multimodal.

A Quarter Century of Work to Revolutionize Architecture, Engineering and Construction Enterprise Information Systems

More than two decades ago, object-oriented representation of AEC （architecture engineering and construction） projects started to offer the promise of seamless communication of semantic data models between computer-based systems used from the design stage to the operation of the facilities. BIM （building information modelling） emerged and appeared as a means to store all relevant data generated during the life-cycle of the facilities. But this upstream view of the built environment, arising from the design and construction stages, extended to the downstream operations where building and industrial facilities appeared more and more as huge dynamic data producers and concentrators while being operated. This created new challenges leading to what is referred to as ISCs （intelligent and smart constructions）. The current state of the art is that final constructions still contain various and increasingly versatile control and service systems, which are hardly standardised, and not interconnected among themselves. Monitoring, maintenance and services are done by specialised companies, each responsible of different systems, which are relying on customised software and techniques to meet specific user needs and are based on monolithic applications that require manual configuration for specific uses, maintenance and support. We demonstrate in this paper that the early promises of integration across the actors and along the life-time of facilities have gone a long way but will only be delivered through enhanced standardisation of computerized models, representations, services and operations still not yet fully accomplished 25 years after work started.

考虑目标谱不确定性及谱形的实际地震动记录优化选取和调整方法

在已有研究成果的基础上,针对基于非线性动力分析的结构抗震性能评估中实际地震动记录的选取和调整进行了研究。为了使地震动输入能够满足工程场点未来可能遭遇的地震危险性水平需求,借助蒙特卡洛模拟方法,考虑地震动谱形的影响,通过生成随机模拟谱来匹配目标谱多元对数正态分布特征,并采用反应谱形参数优化了地震动记录的选取和调整方法。与通常采用的确定性地震动选取方法相比,所提出的方法能够有效匹配目标谱均值、标准差和谱相关性,较好地反映地震危险性水平本身的不确定特征,且具有较高的选取效率和匹配精度。鉴于目标谱不确定性对结构易损性分析结果的重要影响,研究成果能够为设定地震环境下结构抗震性能评估提供合理可靠的方法依据。

PSEUDO ALMOST PERIODIC SOLUTIONS OF DIFFERENTIAL EQUATIONS WITHPIECEWISE CONSTANT ARGUMENT

The authors discuss the existence of pseudo almost periodic solutions of differential equations with piecewise constant argument by means of introducing new concept, pseudo almost periodic sequence.