DVA在通信中的应用及前景展望

介绍ＤＶＡ所具有的性能特点和它与外部设备的连接方式,依据其良好的适应性提出它在电力系统通信中的应用设想。     

Distant Recurrence of a Cerebral Cavernous Malformation in the Vicinity of a Developmental Venous Anomaly: Case Report of Local Oxy-Inflammatory Events

Background: Cerebral cavernous malformations (CCMs) are a major type of cerebrovascular lesions of proven genetic origin that occur in either sporadic (sCCM) or familial (fCCM) forms, the latter being inherited as an autosomal dominant condition linked to loss-of-function mutations in three known CCM genes. In contrast to fCCMs, sCCMs are rarely linked to mutations in CCM genes and are instead commonly and peculiarly associated with developmental venous anomalies (DVAs), suggesting distinct origins and common pathogenic mechanisms. Case report: A hemorrhagic sCCM in the right frontal lobe of the brain was surgically excised from a symptomatic 3 year old patient, preserving intact and pervious the associated DVA. MRI follow-up examination performed periodically up to 15 years after neurosurgery intervention demonstrated complete removal of the CCM lesion and no residual or relapse signs. However, 18 years after surgery, the patient experienced acute episodes of paresthesia due to a distant recurrence of a new hemorrhagic CCM lesion located within the same area as the previous one. A new surgical intervention was, therefore, necessary, which was again limited to the CCM without affecting the pre-existing DVA. Subsequent follow-up examination by contrast-enhanced MRI evidenced a persistent pattern of signal-intensity abnormalities in the bed of the DVA, including hyperintense gliotic areas, suggesting chronic inflammatory conditions. Conclusions: This case report highlights the possibility of long-term distant recurrence of hemorrhagic sCCMs associated with a DVA, suggesting that such recurrence is secondary to focal sterile inflammatory conditions generated by the DVA.     

Random vibrations of a structure modified by damped absorbers

The problem of reducing the level of vibrations in various constructions has been considered for many years. This is an important element of analyzing the technical condition of buildings and the comfort of users. Various ways and means of preventing unacceptable vibrations are known and the search for an optimal absorber is still ongoing. Different kinds of vibration absorbers are applied for reducing the vibration level in various engineering structures. Vibrations caused by traffic do not pose a threat to a structure, but are often a nuisance for people. There is a need to reduce them, especially in cities where there is more traffic. In order to be able to analyze an excited structure, traffic was modeled. A model that is a structure and an absorber system with two degrees of freedom is proposed in the paper. The first eigenfrequency of the structure was included in the analysis. As a result, the authors obtained closed equations of motion. The work examines the problem of the absorber effect on the vibrations of traffic-induced structures. It was assumed that the shocks occurring at random moments, and which form the Poisson process, are determined by random amplitude, a deterministic shape function and two different forms of envelope functions. The problem was discussed in the field of correlation theory and spectral density function. Numerical analysis of the displacement of the two-degree system is considered.     

动力吸振器在车辆振动控制中的应用

在探讨动力吸振器设计方法的基础上,设计了一阻尼式动力吸振器ＤＶＡ（ＤｙｎａｍｉｃＶｉｂｒａｔｉｏｎＡｂｓｏｒｂｅｒ）,并将其应用于某轻型客车的动力传动系统中。试验证明,该动力吸振器能有效地控制该车动力总成的弯曲振动。     

A portable device for the assessment of dynamic visual acuity

Dynamic visual acuity (DVA) thresholds are among the few visual functions predictive of automobile crashes. DVA is also sensitive to alcohol and aging. However, measuring DVA is awkward because there is no standardized, efficient, flexible apparatus for DVA assessment. In this project, we developed a prototype of an automated, portable DVA system using a low-energy laser, and we compared this laser DVA with the traditional device in two within-subjects, repeated measures designs. The two studies included 48 participants (22 males and 26 females with an average age of 18.33 years). The most important findings were that: (1) retest reliabilities of the two DVA devices were comparable and higher with the laser; (2) average correlations between the two devices were r = 0.62 (p < 0.01) and r = 0.65 (p < 0.01) for the two designs respectively; and (3) after correction for reliability attenuation these improved to r = 0.92 and r = 0.78. These findings indicate that a flexible DVA laser device can be developed to measure the same construct as the more traditional bulky DVA device.     

城轨车辆车体多重动力吸振器减振方法研究

为了让动力吸振器在降低轨道车辆车体振动的同时能够更好的适应车下剩余空间,根据多重动力吸振器原理,针对城轨车辆运行的特点,建立了包含多重动力吸振器的轨道车辆垂向振动模型,提出了适用于城市轨道车辆车体多重动力吸振器的设计方法。①讨论了载客量和速度变化对多重动力吸振器的减振性能的影响,指出了传统多重动力吸振器的局限性;②针对轨道车辆振动频率变化频繁的特点,提出了多重动力吸振器的目标频率的优化方法,从而避免了增振的情况出现;③以四条典型城市轨道线路为算例,利用DVA减振指标进行评价,分别获得了不同线路的车体多重动力吸振器的最优目标频率,并验证了该优化方法的有效性。研究结果表明:相同附加质量下,多重动力吸振器对车体的吸振能力要优于单个动力吸振器,考虑到实际的应用,在车体安装四重动力吸振器是较为适宜的选择;经过优化的多重动力吸振器在整个速度区间都能起到很好的减振效果,能够有效避免增振现象的发生;多重动力吸振器的目标频率的设计要针对不同的线路进行调整,特定线路需要特定设计才能发挥出最佳减振能力。该研究的工作为车体多重动力吸振器的研究和应用提供了参考依据。     

动力吸振器在动力总成弯曲振动控制中应用的研究

汽车动力传动系的弯曲振动不仅会影响乘坐舒适性，而且会引起车辆零部件的早期损坏。该文在探讨动力吸振器设计方法的基础上，设计了一阻尼式动力吸报器DVA（DynamicVibrationAbsorber），并将其安装到某轻型客车的动力传动系中。试验证明，动力吸振器能有效地控制该车动力总成的弯曲振动。     

Application of DVA theory in vibration reduction of carbody with suspended equipment for high-speed EMU

The theory of dynamic vibration absorber (DVA) was applied to restrain the vibration of carbody for high-speed electric multiple unit (EMU). The carbody was modeled as an Euler-Bernoulli beam with the equipment mounted on the chassis regarded as a DVA. Suspension parameters of the equipment were optimized based on the modal analysis of the beam and parameter optimization of the DVA. Vertical motion equations of the carbody and equipment were derived to study the effect of the suspension parameters on the vibration of carbody, which included the suspension frequency, damping ratio, mounting position and mass. Then a 3D rigid-flexible coupled vehicle system dynamics model was built to simulate the response of carbody and equipment to track excitation. The results show that the equipment mounted on the carbody chassis can be regarded as a DVA to reduce the flexible vibration of carbody, and the optimum suspension frequency can be calculated theoretically with the first-order vertical bending mode of carbody considered. Heavy equipment should be mounted to the carbody center as close as possible to obtain a significant vibration reduction, while light equipment has quite limited contribution to that. Also, a laboratory test was conducted on the full-scale test rig which shows a good agreement with the theoretical analysis and dynamic simulations. The faster the vehicle runs, the more significant are the advantages of the elastic suspension.     

转向盘动力吸振器稳健性设计研究与应用

为解决怠速时转向盘振动大问题,用基于稳健性的设计方法,开发了动力吸振器(dynamic vibration ab-sorber,DVA).采用最小二乘迭代法,识别出动力吸振器安装位置的等效参数,运用基于6sigma多目标稳健性优化方法,进行动力吸振器的参数的优化.在样件制作前用有限元仿真预测其固有频率,用激振台测出其固...