Development of an experimental methodology to evaluate the influence of a bamboo frame on the bicycle ride comfort

In the current environment of increased emphasis on sustainable transport, there is manifold increase in the use of bicycles for urban transport. One concern which might restrict the use is the ride comfort and fatigue. There has been limited research in addressing the difficulty in bicycle ride comfort quantification. The current study aims to develop a methodology to quantify bicycle discomfort so that performance of bicycles constructed from bamboo and aluminium alloy can be compared. Experimentally obtained frequency response functions are used to establish a relation between the road input and the seat and rider response. A bicycle track input profile based on standard road profiles is created so as to estimate the acceleration responses. The whole-body-vibration frequency weighting is applied to quantify the perception of vibration intensity so that eventual discomfort ranking can be obtained. The measured frequency response functions provide an insight into the effect of frame dynamics on the overall resonant behaviour of the bicycles. The beneficial effect of frame compliance and damping on lower modes of vibration is very clear in the case of bamboo frame, in turn affecting seat and rider response. In the bamboo frame, because of multiple resonances, the frequency response of the handlebar is smaller at higher frequencies suggesting effective isolation. Further improvements may have come from the joints made from natural composites. Overall, based on the comparative analysis and the methodology developed, bamboo frame shows significant improvement in ride comfort performance compared with the aluminium frame.     

新型装配式施工平台的设计研究

设计出一种托架可调节,能应用于不同步距支架平台施工的新型装配式施工平台.该施工平台由可调节式托架、可伸缩式防护栏杆和插销式扣件3部分组成,结构简单,安装拆除安全方便,可循环应用于各种施工平台,因而能大大降低施工成本,缩短施工工期.     

一种改进的约束阻尼梁振动解析模型

在目前已有的模型基础上提出一种改进的约束阻尼的梁振动解析模型。目前主要的约束阻尼解析模型都是假设阻尼层的剪切变形为唯一的阻尼来源，但是其他的变型，包括阻尼层以及约束层的纵向和横向的拉伸压缩也都是阻尼的重要来源。因此，将所有可能的阻尼变形包括剪切、拉伸和压缩集成到一个解析模型里面。这个改进的解析模型可以用来计算多层阻尼结构的自然频率和损耗因子。数值分析验证了此解析模型可以准确地预测结构的动态特性，所以此模型可以被广泛地采用在多层约束阻尼结构预测和设计等实际运用上。     

罗经回路在船用航姿系统中的应用与工程实现

由惯性导航原理的特性可知,纯惯性无阻尼航姿系统的误差将出现明显的周期性振荡,并随时间发散,如水平姿态误差体现出傅科周期调制舒勒周期振荡,方位误差体现出地球周期振荡.若在水平回路中加入阻尼网络,可使其舒勒周期振荡衰减,傅科周期振荡也将随之消失,再加入方位阻尼,就能完成内全阻尼网络的设计.文章将平台精对准中罗经回路的思想引入到捷联航姿系统中,并通过改变原有航姿算法以达到内全阻尼的目的,最后的数字仿真结果表明,该新算法可使航姿系统不依赖任何外部信息就能使姿态精度得到提高.     

阻尼材料在铁路客车噪声控制中的试验研究

简单介绍了铁路客车内部噪声的实测情况。分析了铁路客车噪声控制中阻尼材料的选择原则和选用阻尼材料的特点，阐述了车体阻尼处理结构的方案设计，并进行了现车试验及其结果分析。     

高速铁路无支座整体式刚构设计

为与相邻公路桥对孔布置并具有较优的结构性能,新建福州至厦门铁路泉州湾跨海大桥引桥采用多联(3×70)m无支座整体式刚构,该桥型全桥不设支座,边墩与中墩均与主梁固结形成整体刚构。该桥主梁采用预应力混凝土箱梁;墩高20~50 m,中墩采用实体墩或空心墩,边墩采用薄壁墩,相邻联边墩共用基础。通过在相邻梁端加装横向限位器、应用无砟轨道小阻尼扣件、边墩顶梁段采用两交界边墩临时固结后悬臂浇筑施工等措施较好地解决了梁端相对横向位移、轨道适应性及海上施工等问题。对该无支座整体式刚构桥结构性能进行分析,结果表明:其各项指标均满足规范要求,具有较好的经济性、抗震性能和景观效果。     

Modelling generalisation and power dissipation of flexible-wheel suspension concept for planetary surface vehicles

Flexible-wheel (FW) suspension concept has been regarded to be one of the novel technologies for future planetary surface vehicles (PSVs). This study develops generalised models for fundamental stiffness and damping properties and power consumption characteristics of the FW suspension with and without considering wheel-hub dimensions. Compliance rolling resistance (CRR) coefficient is also defined and derived for the FW suspension. Based on the generalised models and two dimensionless measures, suspension properties are analysed for two FW suspension configurations. The sensitivity analysis is performed to investigate the effects of the design parameters and operating conditions on the CRR and power consumption characteristic of the FW suspension. The modelling generalisation permits analyses of fundamental properties and power consumption characteristics of different FW suspension designs in a uniform and very convenient manner, which would serve as a theoretical foundation for the design of FW suspensions for future PSVs.     

SS4G型电力机车牵引绕组阻尼电路参数分析

通过对SS4G型电力机车牵引绕组阻尼电路参数的计算，分析了阻尼电路频繁损坏的可能原因，并归纳了阻尼电路参数的计算方法，最后提出了阻尼电路参数的改进建议。     

扁平箱梁颤振后状态的振幅依存性研究

以舟岱通道大桥扁平箱梁断面为对象，通过节段模型风洞试验详细测试了该断面在风速超过颤振临界点后，振幅随风速变化的颤振后振动特性。基于变振幅的运动时程，阐释了气动阻尼、相位差及颤振导数等参数的振幅依存特性，提出了变振幅条件下的各参数的识别方法，指出了影响扁平箱梁颤振后特性的主要因素，并利用耦合颤振闭合解法进行了验证。研究结果表明：扁平箱梁在颤振后的振动过程中，气动阻尼具有明显的振幅依存性，相位差的振幅依存性较弱，振幅比基本不具有振幅依存性；颤振导数A₂^*随振幅变化而显著变化，是影响气动阻尼改变的最主要因素，其余颤振导数具有一定的振幅依存性，但对气动阻尼的影响较小。最后从气动阻尼随振幅变化的角度初步阐释了扁平箱梁在颤振后发生不同振动现象的动力学机理，并从气动阻尼曲线存在多个零点的角度解释了扁平箱梁在同一风速下具有多个稳定振幅点的可能性。     

OV 模型交通流阻尼特性研究

对交通流跟驰模型施以拉氏变换（或z 变换）,转换为控制系统传递函数形式, 进而通过分析传递函数来探讨交通流系统稳定性及控制方法,这是交通流稳定性理论研 究重要方向之一.为进一步挖掘分析稳定交通流系统在稳定状态下动态特性,基于最优速 度跟驰模型,以控制理论时域分析方法,研究了交通流系统在欠阻尼和过阻尼两种情况 下阶跃响应动态特性,并以仿真算例验证了理论正确性.过阻尼较欠阻尼交通流系统稳定 性好,但调节时间更长,若将交通事件抽象为阶跃响应,通过分析交通流系统调节时间、 超调量等参数,可为计算交通事件持续时间作参考,进而制定合理有效的交通管理措施.