地铁列车运营引起的环境问题

指出了地铁振动产生的原因及其影响，分析了影响振动的主要参数及振动的规律，并提出了一些行之有效的减振隔振降噪措施，从而为在已有地铁设计新建筑物时或在已有建筑物条件下设计地铁提供一些有参考价值的资料，同时对地铁系统的防振减灾设计也有一定的帮助。     

Do Scaphoideus titanus (Hemiptera: Cicadellidae) nymphs use vibrational communication?

Small Auchenorrhyncha use substrate-borne vibrations to communicate. Although this behaviour is well known in adult leafhoppers, so far no studies have been published on nymphs. Here we checked the occurrence of vibrational communication in Scaphoideus titanus (Hemiptera: Cicadellidae) nymphs as a possible explanation of their aggregative distributions on host plants. We studied possible vibratory emissions of isolated and grouped nymphs, as well as their behavioural responses to vibration stimuli that simulated presence of conspecifics, to disturbance noise, white noise and predator spiders. None of our synthetic stimuli or pre-recorded substrate vibrations from nymphs elicited specific vibration responses and only those due to grooming or mechanical contacts of the insect with the leaf were recorded. Thus, S. titanus nymphs showed to not use species-specific vibrations neither for intra- nor interspecific communication and also did not produce alarm vibrations when facing potential predators. We conclude that their aggregative behaviour is independent from a vibrational communication.     

Social waves in giant honeybees (Apis dorsata) elicit nest vibrations

Giant honeybees (Apis dorsata) nest in the open and have developed a wide array of strategies for colony defence, including the Mexican wave-like shimmering behaviour. In this collective response, the colony members perform upward flipping of their abdomens in coordinated cascades across the nest surface. The time–space properties of these emergent waves are response patterns which have become of adaptive significance for repelling enemies in the visual domain. We report for the first time that the mechanical impulse patterns provoked by these social waves and measured by laser Doppler vibrometry generate vibrations at the central comb of the nest at the basic (=‘natural’) frequency of 2.156?±?0.042 Hz which is more than double the average repetition rate of the driving shimmering waves. Analysis of the Fourier spectra of the comb vibrations under quiescence and arousal conditions provoked by mass flight activity and shimmering waves gives rise to the proposal of two possible models for the compound physical system of the bee nest: According to the elastic oscillatory plate model, the comb vibrations deliver supra-threshold cues preferentially to those colony members positioned close to the comb. The mechanical pendulum model predicts that the comb vibrations are sensed by the members of the bee curtain in general, enabling mechanoreceptive signalling across the nest, also through the comb itself. The findings show that weak and stochastic forces, such as general quiescence or diffuse mass flight activity, cause a harmonic frequency spectrum of the comb, driving the comb as an elastic plate. However, shimmering waves provide sufficiently strong forces to move the nest as a mechanical pendulum. This vibratory behaviour may support the colony-intrinsic information hypothesis herein that the mechanical vibrations of the comb provoked by shimmering do have the potential to facilitate immediate communication of the momentary defensive state of the honeybee nest to the majority of its members.     

金属材料的超声塑性加工

此文介绍了超声振动在金属塑性加工领域的应用,讨论了超声塑性加工的理论机制和工艺特点,论述了超声场中的材料性能和粘塑性本构关系。     

Remote monitoring of vibrational information in spider webs

Spiders are fascinating model species to study information-acquisition strategies, with the web acting as an extension of the animal’s body. Here, we compare the strategies of two orb-weaving spiders that acquire information through vibrations transmitted and filtered in the web. Whereas Araneus diadematus monitors web vibration directly on the web, Zygiella x-notata uses a signal thread to remotely monitor web vibration from a retreat, which gives added protection. We assess the implications of these two information-acquisition strategies on the quality of vibration information transfer, using laser Doppler vibrometry to measure vibrations of real webs and finite element analysis in computer models of webs. We observed that the signal thread imposed no biologically relevant time penalty for vibration propagation. However, loss of energy (attenuation) was a cost associated with remote monitoring via a signal thread. The findings have implications for the biological use of vibrations by spiders, including the mechanisms to locate and discriminate between vibration sources. We show that orb-weaver spiders are fascinating examples of organisms that modify their physical environment to shape their information-acquisition strategy.     

How do animals use substrate-borne vibrations as an information source?

Animal communication is a dynamic field that promotes cross-disciplinary study of the complex mechanisms of sending and receiving signals, the neurobiology of signal detection and processing, and the behaviors of animals creating and responding to encoded messages. Alongside visual signals, songs, or pheromones exists another major communication channel that has been rather neglected until recent decades: substrate-borne vibration. Vibrations carried in the substrate are considered to provide a very old and apparently ubiquitous communication channel that is used alone or in combination with other information channels in multimodal signaling. The substrate could be ‘the ground’, or a plant leaf or stem, or the surface of water, or a spider’s web, or a honeybee’s honeycomb. Animals moving on these substrates typically create incidental vibrations that can alert others to their presence. They also may use behaviors to create vibrational waves that are employed in the contexts of mate location and identification, courtship and mating, maternal care and sibling interactions, predation, predator avoidance, foraging, and general recruitment of family members to work. In fact, animals use substrate-borne vibrations to signal in the same contexts that they use vision, hearing, touch, taste, or smell. Study of vibrational communication across animal taxa provides more than just a more complete story. Communication through substrate-borne vibration has its own constraints and opportunities not found in other signaling modalities. Here, I review the state of our understanding of information acquisition via substrate-borne vibrations with special attention to the most recent literature.     

Infrared spectroscopic probing of dimethylamine clusters in an Ar matrix

Amines have many atmospheric sources and their clusters play an important role in aerosol nucleation processes. Clusters of a typical amine, dimethylamine (DMA), of different sizes were measured with matrix isolation IR (infrared) and NIR (near infrared) spectroscopy. The NIR vibrations are more separated and therefore it is easier to distinguish different sizes of clusters in this region. The DMA clusters, up to DMA tetramer, have been optimized using density functional methods, and the geometries, binding energies and thermodynamic properties of DMA clusters were obtained. The computed frequencies and intensities of NH-stretching vibrations in the DMA clusters were used to interpret the experimental spectra. We have identified the fundamental transitions of the bonded NH-stretching vibration and the first overtone transitions of the bonded and free NH-stretching vibration in the DMA clusters. Based on the changes in vibrational intensities during the annealing processes, the growth of clusters was clearly observed. The results of annealing processes indicate that DMA molecules tend to form larger clusters with lower energies under matrix temperatures, which is also supported by the calculated reaction energies of cluster formation.     

喷水对火箭射流噪声的影响研究

火箭噪声将对运载火箭的载荷、结构、地面设施产生极为不利的影响,针对火箭发射时所产生的强噪声问题,通过分析火箭射流噪声的气动特性,利用喷水试验和有限体积计算方法获得喷水对射流噪声的降噪量,得到了喷水质量流率对有效燃气参数的影响规律,为发射台的设计提供了技术依据。     

内爆炸载荷作用下爆炸容器振动响应试验研究

为研究具有密闭结构的装备、建筑物或地下工事在内爆炸载荷作用下的冲击振动响应,通过某一尺寸爆炸容器的冲击振动环境试验构建内爆炸振源模型和密闭结构响应模型,比较测量了几个典型位置在不同强度载荷下的振动情况并进行频谱分析,提出了基于振动主频的判断结构损伤和防止共振响应的方法,并对试验数据进行数值拟合,弄清振动参数在结构上的衰...     

When males whistle at females: complex FM acoustic signals in cockroaches

Male cockroaches of the species Elliptorhina chopardi expel air through a pair of modified abdominal spiracles during courtship. This air expulsion simultaneously produces air and substrate-borne vibrations. We described and compared in details these two types of vibrations. Our analysis of the air-borne signals shows that males can produce three categories of signals with distinct temporal and frequency parameters. “Pure whistles” consist of two independent harmonic series fast frequency modulated with independent harmonics that can cross each other. “Noisy whistles” also possess two independent voices but include a noisy broad-band frequency part in the middle. Hiss sounds are more noise-like, being made of a broad-band frequency spectrum. All three call types are unusually high in dominant frequency (>5 kHz) for cockroaches. The substrate-borne signals are categorised similarly. Some harmonics of the substrate-borne signals were filtered out, however, making the acoustic energy centered on fewer frequency bands. Our analysis shows that cockroach signals are complex, with fast frequency modulations and two distinct voices. These results also readdress the question of what system could potentially receive and decode the information contained within such complex sounds.Electronic supplementary material  Supplementary material is available for this article at and is accessible for authorized users.     

Comparison of pollination and defensive buzzes in bumblebees indicates species-specific and context-dependent vibrations

Bees produce vibrations in many contexts, including for defense and while foraging. Buzz pollination is a unique foraging behavior in which bees vibrate the anthers of flowers to eject pollen which is then collected and used as food. The relationships between buzzing properties and pollen release are well understood, but it is less clear to what extent buzzing vibrations vary among species, even though such information is crucial to understanding the functional relationships between bees and buzz-pollinated plants. Our goals in this study were (1) to examine whether pollination buzzes differ from those produced during defense, (2) to evaluate the similarity of buzzes between different species of bumblebees (Bombus spp.), and (3) to determine if body size affects the expression of buzzing properties. We found that relative peak amplitude, peak frequency, and duration were significantly different between species, but only relative peak amplitude differed between pollination and defensive buzzes. There were significant interactions between species and buzz type for peak frequency and duration, revealing that species differed in their patterns of expression in these buzz properties depending on the context. The only parameter affected by body size was duration, with larger bees producing shorter buzzes. Our findings suggest that although pollination and defensive buzzes differ in some properties, variability in buzz structure also exhibits a marked species-specific component. Species differences in pollination buzzes may have important implications for foraging preferences in bumblebees, especially if bees select flowers best matched to release pollen for their specific buzzing characteristics.     

绿色通讯:现代通讯的方向性标志

在这个高度信息化的时代，通讯已经深入到了社会、生活的许多方面，而且正逐渐成中的重要元素影响或操纵着我们的生活。可以说有人的地方就有通讯网络的覆盖，因为我们每天都已经无法离开通讯了。就通讯的发展而言．它经过了一个漫长的过程．从秦时的烽火狼烟到今天的移动通讯技术，通讯以一种不可思议的角度切入到了我们的生活中并以一种你无法拒绝的方式正在改变着我们的生活。     

Utilisation of bubble resonance phenomena to improve gas–liquid contact

 In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned, the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with minimal energy input. Received: 7 July 2000 / Accepted in revised form: 28 August 2000     

浅谈管道隔振

在建筑工程中管道系统作为介质输送的必备条件,虽然管道自身不会产生振动,但是管道在与相关振动设备连接时则变成了传递振动的"振桥",在隔振设计时经常被忽视。本文主要讲述了冷冻机房内水管路吊挂,落地安装及通风系统中风管吊装时的几种减振降噪做法,还包括了经常被大家忽视的管道穿墙隔振的做法,分别通过添加弹簧减振器、弹簧吊架、橡胶减振垫、橡胶挠性接管、金属软管、波纹管补偿器等减振器材,使得振源通过管道产生振动的传导大大降低,并且记述了一些减振设备在安装时应注意的事项。     

两级A/O工艺处理焦化废水有机污染物转化特征及细菌群落响应

为探究两级缺氧/好氧(anoxic/oxic, A/O)工艺处理焦化废水有机污染物转化和细菌群落结构之间的关系,以实际运行的焦化废水处理厂为研究对象,采用傅里叶变换红外光谱和三维荧光光谱对废水中有机污染物官能团与溶解性有机物(dissolved organic matter, DOM)进行分析,并采用高通量测序技术,分析两级A/O工艺中细菌群落结构及其功能的沿程变化. 结果表明:①两级A/O工艺对化学需氧量(COD)、氨氮(NH₄+-N)、硫氰酸盐(SCN?)、苯并[a]芘(BaP)、苯酚、挥发酚的去除率均在90%以上. ②各有机污染物的去除与醇类、脂类、醚类、多糖类及羧酸类等物质的C≡N、C—N、C=C、—CO—伸缩振动,以及—NH₂和N—H弯曲振动等官能团运动有关,原水中大部分DOM被去除. ③微生物分析表明,硫杆菌(Thiobacillus)为两级A/O工艺的优势菌属(相对丰度为18.85%~31.06%),Fluviicola和norank_f_JG30-KF-CM45的相对丰度与BaP浓度均呈负相关,Arenimonas的相对丰度与挥发酚、苯酚浓度均呈正相关,Bradyrhizobium、Nakamurella、Nitrospira、norank_f_NS9_marine_group、unclassified_f_Rhizobiaceae的相对丰度与挥发酚、苯酚浓度均呈负相关. ④两级A/O工艺中有机污染物的去除与氟苯甲酸酯降解、多环芳烃降解、苯甲酸酯降解等多种代谢途径有关. 研究显示,经两级A/O工艺处理后,焦化废水中的主要污染物均显著去除,并且有机污染物变化均会影响功能微生物相对丰度的改变.      

Asymmetries in commitment in an avian communication network

Mobbing of predators occurs within a conspecific and heterospecific context but has not been quantified within the framework of a communication network and analysed with respect to heterospecific reciprocity. Here, we used playbacks of mobbing calls to show that mobbing is unequally distributed within a community of deciduous forest birds. Five species (great tit Parus major, blue tit Cyanistes caeruleus, marsh tit Poecile palustris, nuthatch Sitta europaea and chaffinch Fringilla coelebs) responded to each other’s playbacks of mobbing calls. Commitment to mob was measured by minimum distance, response latency and uttering of calls. Commitment was higher when conspecific calls were broadcast. Yet, responses to heterospecific calls were significantly different between the five species. Chaffinches had the lowest commitment, and blue tits tended to have the highest. The communication network is asymmetric. Some species invest more than they receive from other species. As mobbing might incur costs, these are unequally distributed across the community.     

Femtosecond time-resolved spectroscopy of elementary molecular dynamics

Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) is applied in order to prepare and monitor laser-induced vibrational coherences (wave packets) of different samples mainly in its electronic ground state but also in excited states. The time evolution of these wave packets gives information on the dynamics of molecular vibrations. In a first example the femtosecond (fs) CARS transients of iodine are investigated. By changing the relative delay between the applied laser pulses of this non-degenerated four-wave mixing technique, both the wavepacket motion on the electronically excited and the ground states can be detected as oscillations in the coherent anti-Stokes signal. Second we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. This selectivity is achieved by varying the phase shape (chirp) and the relative delay between the exciting laser pulses.     

Surface roughness prediction in milling based on tool displacements

In this paper, an experimental device using non-contact displacement sensors for the investigation of milling tool behaviour is presented. It enables the recording of high frequency tool vibrations during milling operations. The aim of this study is related to the surface topography prediction using tool displacements and based on tool center point methodology. From the recorded signals and the machining parameters, the tool deformation is modeled. Then, from the calculated deflection, the surface topography in 3D can be predicted. In recent studies, displacements in XY plane have been measured to predict the surface topography in flank milling. In this article, the angular deflection of the tool is also considered. This leads to the prediction of surfaces obtained in flank milling as well as in end milling operations. Validation tests were carried out: the predicted profiles were compared to the measured profile. The results show that the prediction corresponds well in shape and amplitude with the measurement.