基于双频超声波技术的导盲实验设计

为提高学生对超声波的实际应用能力,在超声波测距技术的基础上,引入广泛应用于海洋探测方法中的双频超声波探测技术设计了一个导盲实验。该导盲系统能够在十几米甚至二十米的范围精确地探测障碍物距离,同时具有大量程与高精度两大优势,且采用太阳能供电,报警装置还可以播报障碍物距离。     

Commercial road vehicle noise

A survey of the characteristics of the noise emitted by commercial vehicles has been made. The most important single parameter determining the noise of a modern diesel-engined vehicle is the engine speed. All of the other parameters such as load, road speed, etc., have only a secondary effect.The sources of noise on the vehicle are reviewed and it is shown how the characteristics of these sources determine the overall noise characteristics of the vehicle. It has been found that a simple model of the vehicle as a number of coincident point sources predicts the overall noise characteristics of the vehicle to ±2 dB(A). It is shown that there are two extremes of behaviour, the rolling noise controlled vehicle and the power unit noise controlled vehicle; the engine is currently the controlling noise source.Tyre noise has been investigated in some detail as comparatively little has been published previously on this source. Empirical relationships between the tyre noise and speed, tyre size and road surface roughness are given. It is concluded that tyre noise is generated by impacting between elements of the tyre tread and elements of the road surface.Modifications have been made to the engine, exhaust, intake and cooling fan of a 9 ton, 6 litre diesel engined truck which have reduced its ISO test noise level from 88 dB(A) to 80 dB(A). However, it is concluded that 80 dB(A) commercial vehicles are not yet feasible for production. In particular insufficient is known about cooling fan design.Finally cab noise has been investigated and it has been found to originate from the same source as the exterior noise, power unit airborne noise. Therefore any modifications to the power unit to reduce exterior noise will have a similar effect on interior noise. This is confirmed by the vehicle modifications mentioned above which reduced the maximum cab noise from 87 dB(A) to 79 dB(A).     

Enabling a high-performance saltwater Al-air battery via ultrasonically driven electrolyte flow

As an emerging battery technology, the Al-air flow battery (AAFB) exhibits high energy density due to the recycling of electrolytes, thus showing great potential as a type of clean and sustainable energy storage system. Conventionally, it employs an external mechanical pump to recycle the electrolyte. In this work, the saltwater AAFB in which the electrolyte is recycled by the ultrasonic capillary effect (rather than a mechanical pump) and the reaction chamber is agitated by ultrasonic vibration, is proposed and investigated. Our numerical simulations show that a travelling ultrasonic wave in the electrolyte flow system causes the capillary flow and agitation. The experimental results show that the percentage increase of the peak power density (relative to that with static electrolyte) can be up to about 7.5 times of that with the electrolyte flow driven by a mechanical pump, under the same electrolyte flow rate and concentration (3.3 ml min⁻¹ and 3 M NaCl). The optimal peak power density, which can be achieved by optimizing the reaction chamber thickness, electrolyte concentration and ultrasonic vibration velocity, is 43.88 mW cm⁻². This work illustrates that the acoustofluidic method can not only improve the discharge performance of the saltwater AAFB effectively, but also greatly decrease the energy consumption, weight and volume of the electrolyte driving unit of the AAFB. In addition, analyses based on experimental results show that the energy gain of a series/parallel battery system formed by multiple identical cells can be larger than one, if the number of cells in the system is large enough.     

Influence of atmospheric refraction on the performance of an outdoor ultrasonic pulse compression system

Nowadays, many ultrasonic sensory systems are being developed to operate outdoors, where they are finding a variety of applications, such as local positioning, vehicle navigation or obstacle detection. To assure the reliable operation of these systems under any meteorological condition, it is necessary to achieve a thorough comprehension of the effects that the different atmospheric phenomena can have on the propagation of these acoustic waves. This paper deals with one of these phenomena, atmospheric refraction, and its influence on the performance of an ultrasonic system whose signals are detected by matched filtering.     

Autoresonant control of nonlinear mode in ultrasonic transducer for machining applications

Experiments conducted in several countries have shown that the improvement of machining quality can be promoted through conversion of the cutting process into one involving controllable high-frequency vibration at the cutting zone. This is achieved through the generation and maintenance of ultrasonic vibration of the cutting tool to alter the fracture process of work-piece material cutting to one in which loading of the materials at the tool tip is incremental, repetitive and controlled. It was shown that excitation of the high-frequency vibro-impact mode of the tool-workpiece interaction is the most effective way of ultrasonic influence on the dynamic characteristics of machining. The exploitation of this nonlinear mode needs a new method of adaptive control for excitation and stabilisation of ultrasonic vibration known as autoresonance. An approach has been developed to design an autoresonant ultrasonic cutting unit as an oscillating system with an intelligent electronic feedback controlling self-excitation in the entire mechatronic system. The feedback produces the exciting force by means of transformation and amplification of the motion signal. This allows realisation for robust control of fine resonant tuning to bring the nonlinear high Q-factor systems into technological application. The autoresonant control provides the possibility of self-tuning and self-adaptation mechanisms for the system to keep the nonlinear resonant mode of oscillation under unpredictable variation of load, structure and parameters. This allows simple regulation of intensity of the process whilst keeping maximum efficiency at all times. An autoresonant system with supervisory computer control was developed, tested and used for the control of the piezoelectric transducer during ultrasonically assisted cutting. The system has been developed as combined analog-digital, where analog devices process the control signal, and parameters of the devices are controlled digitally by computer. The system was applied for advanced machining of aviation materials.     

Food drying process by power ultrasound

Drying processes, which have a great significance in the food industry, are frequently based on the use of thermal energy. Nevertheless, such methods may produce structural changes in the products. Consequently, a great emphasis is presently given to novel treatments where the quality will be preserved. Such is the case of the application of high-power ultrasound which represents an emergent and promising technology. During the last few years, we have been involved in the development of an ultrasonic dehydration process, based on the application of the ultrasonic vibration in direct contact with the product. Such a process has been the object of a detailed study at laboratory stage on the influence of the different parameters involved. This paper deals with the development and testing of a prototype system for the application and evaluation of the process at a pre-industrial stage. Such prototype is based on a high-power rectangular plate transducer, working at a frequency of 20 kHz, with a power capacity of about 100 W. In order to study mechanical and thermal effects, the system is provided with a series of sensors which permit monitoring the parameters of the process. Specific software has also been developed to facilitate data collection and analysis. The system has been tested with vegetable samples.     

超声波加工盲孔的研究

本文以超声波加工机对玻璃等硬脆材料元件的加工工艺为主要研究对象,阐述了超声波加工的原理、变幅杆和刀具的设计以及加工工艺的研究,并将它应用在空间光学系统中光学元件的轻量化的加工。同时对加工后的表面微观特性——表面微裂纹和表面微应力进行具体测试分析,以解决在复杂的空间环境中元件的表面质量对使用精度和应力变形的影响,从而提出适于大型光学元件轻量化的工艺技术方法。     

A simulation model for ultrasonic pulse-echo systems

Echo patterns obtained by using an ultrasonic pulse-echo system are mainly determined by the structure of an object, but are influenced by many other factors such as the directivity and damping characteristics of the ultrasonic transducer, the dynamic range of the display unit and so on. A simulation model has been developed in which if these factors are specified numerically and fed to the simulator, then an A- or B-mode display pattern is obtained as its output. In this paper the principles of the simulator are presented first and some results of the simulation are given and they are compared with echo patterns obtained experimentally.     

Energetic study of ultrasonic wettability enhancement

Many industrial and biological interfacial processes, such as welding and breathing depend directly on wettability and surface tension phenomena. The most common methods to control the wettability are based on modifying the properties of the fluid or the substrate. The present work focuses on the use of high-frequency acoustic waves (ultrasound) for the same purpose. It is well known that ultrasound can effectively clean a surface by acoustic cavitation, hence ultrasonic cleaning technology. Besides the cleaning process itself, many authors have observed an important wettability enhancement when liquids are exposed to low and high (ultrasonic) frequency vibration. Ultrasound goes one step further as it can instantly adjust the contact angle by tuning the vibration amplitude, but there is still a lack of comprehension about the physical principles that explain this phenomenon. To shed light on it, a thermodynamic model describing how ultrasound decreases the contact angle in a three-phase wetting system has been developed. Moreover, an analytical and experimental research has been carried out in order to demonstrate that ultrasound is an important competitor to surfactants in terms of energy efficiency and environmental friendliness.     

超声雾化进样技术在ICP-AES中的应用研究

研究了超声雾化进样系统在电感耦合等离子体原子发射光谱(ICP-AES)中的应用,考察了测定的影响因素。结果表明,超声雾化进样条件下,影响谱线强度和测量精密度的因素较多。其中影响较大的因素主要有:载气流量、进样速度、进样时间、冲洗条件及溶液的介质条件。载气的最大允许量远小于气动雾化中的常规用量。同时,进样时间对测量精密度的影响较大,而积分时间对测定的影响较小。此外,冲洗条件对记忆时间的影响较大, 辅助冲洗水流的方式有助于减小记忆效应的影响。实验表明:超声雾化进样条件下,As,Pb,Se,Bi,Ge,Mo,Cd,Cu等八种元素的检出限低于气动雾化进样的检出限10～25倍,超声雾化进样技术在ICP-AES中的应用有助于改善ICP-AES测定的灵敏度。     

The optimisation of ultrasonic cleaning procedures for dairy fouled ultrafiltration membranes

Ultrafiltration (UF) of whey is a major membrane based process in the dairy industry. However, commercialization of this application has been limited by membrane fouling, which has a detrimental influence on the permeation rate. There are a number of different chemical and physical cleaning methods currently used for cleaning a fouled membrane. It has been suggested that the cleaning frequency and the severity of such cleaning procedures control the membrane lifetime. The development of an optimal cleaning strategy should therefore have a direct implication on the process economics. Recently, the use of ultrasound has attracted considerable interest as an alternative approach to the conventional methods. In the present study, we have studied the ultrasonic cleaning of polysulfone ultrafiltration membranes fouled with dairy whey solutions. The effects of a number of cleaning process parameters have been examined in the presence of ultrasound and results compared with the conventional operation. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath. Results show that ultrasonic cleaning improves the cleaning efficiency under all experimental conditions. The ultrasonic effect is more significant in the absence of surfactant, but is less influenced by temperature and transmembrane pressure. Our results suggest that the ultrasonic energy acts primarily by increasing the turbulence within the cleaning solution.     

面向水下应用的电容式微机械超声换能器*

电容式微机械超声换能器具有宽频带和易于制造二维阵列等优势,已经成为一种重要的新型超声换能器。该文针对图像声呐系统对新型超声换能器的迫切需求,提出了一种电容式微机械超声换能器结构和参数,并利用硅微加工技术制备出了该换能器,最后对其主要性能参数进行了测试和分析。测试结果表明该换能器具有发射和接收超声波的功能,中心工作频率为1.965 MHz,6 dB相对带宽达到109.4%,在1 MHz、2 MHz和3 MHz频率时的接收灵敏度分别为-218.29 d B、-219.39 dB和-218.11 dB。该文研制的电容式微机械超声换能器显示出了优秀的宽频带特性,且工作频率和接收灵敏度性能均基本满足了高频图像声呐系统的需求。     

Visible light communication system based on spread spectrum technology for intelligent transportation

In recent years, with the rapid development of the solid state Light emitting diodes (LED’s) material, visible light communication has vast applications in transportation system. Generally, LED visible light communication refers to the communication technology which utilizes LED as a signal transmitter, the air as a transmission medium, and the photodiode as a signal receiving component. Visible light communication based on LED light source has been widespread concerned in intelligent transportation system (ITS). In particular, it is used to solve the communication problems between traffic lights and vehicles. However, signal source switching always puzzles the application of visible light communication based on LED in ITS. If signal source switching is not solved effectively, it will result in the interruption of information transmission. The paper proposes a visible light communication system using spread spectrum technology and pulse position modulation. When the vehicle is at the crossroads, the receiver on the vehicle receives signals from the four LED traffic lights at the same time. During the movement of the vehicle, the peak value of the four signals received by the receiver is constantly changing. The receiver detects the relevant peaks from the four traffic light signals and communicates with the traffic lights which have the maximum correlation peak. The problem of signal source switching is solved effectively. The experimental results show that the proposed system can achieve seamless switching between four-way LED traffic lights at the crossing, and the bit error rate of the system is 10^?4–10^?7.     

菲涅尔透镜聚焦声泳打印装置设计及实验研究*

针对现有的喷墨打印技术需根据喷印材料的特性定制而较难直接用于不同材料打印的问题,设计了一种基于菲涅尔透镜聚焦的声泳打印装置,该装置由超声发生器、超声换能器、菲涅尔透镜以及供液系统组成。首先,利用COMSOL软件模拟液滴在声辐射力作用下的滴落过程,并分析了超声发生器功率、喷嘴到基底距离、菲涅尔透镜厚度等参数对声场压力分布的影响,以及声场压力、喷嘴直径及材料粘度对液滴喷射过程的影响。其次,采用构建的声泳打印装置进行喷射成滴实验,通过调整超声发生器输出功率实现了不同粘度的聚乙二醇溶液的喷射以及UV胶的喷射。实验结果表明：该微滴喷射系统能产生一致性较好的微滴,喷印出的微透镜尺寸波动范围在2%以内,证明了该装置的稳定性以及实现了不同材料微滴喷射的可行性。     

Measurement of hydroxyl radical production in ultrasonic aqueous solutions by a novel chemiluminescence method

Measurement methods for ultrasonic fields are important for reasons of safety. The investigation of an ultrasonic field can be performed by detecting the yield of hydroxyl radicals resulting from ultrasonic cavitations. In this paper, a novel method is introduced for detecting hydroxyl radicals by a chemiluminescence (CL) reaction of luminol-hydrogen peroxide (H2O2)-K5[Cu(HIO6)2](DPC). The yield of hydroxyl radicals is calculated directly by the relative CL intensity according to the corresponding concentration of H2O2. This proposed CL method makes it possible to perform an in-line and real-time assay of hydroxyl radicals in an ultrasonic aqueous solution. With flow injection (FI) technology, this novel CL reaction is sensitive enough to detect ultra trace amounts of H2O2 with a limit of detection (3sigma) of 4.1 x 10(-11) mol L(-1). The influences of ultrasonic output power and ultrasonic treatment time on the yield of hydroxyl radicals by an ultrasound generator were also studied. The results indicate that the amount of hydroxyl radicals increases with the increase of ultrasonic output power (< or = 15 W mL(-1)). There is a linear relationship between the time of ultrasonic treatment and the yield of H2O2. The ultrasonic field of an ultrasonic cleaning baths has been measured by calculating the yield of hydroxyl radicals.     

Advances in ultrasonic production units for enhanced oil recovery in China

With the development of oil recovery technology, ultrasonic technology has been involved in oil production and oilfield development. The mechanism of ultrasonic wave plugging in near well is different from the conventional oil recovery technology. Ultrasonic oil production technique is an effective method to enhance oil production with low cost, good applicability, and no environmental pollution. The core part of ultrasonic oil production equipment for Enhanced Oil Recovery is a high-power ultrasonic transducer. The continuous high-power ultrasound is used to treat the reservoir, which changes the pore structure, the physical property and the state of the fluid, thus improving the permeability and flows conditions of the reservoir, and increasing the oil yield and oil recovery. Ultrasonic oil recovery equipment includes the generation of high-power ultrasonic signals, long-distance transmission and the conversion of electrical energy to acoustic energy. In this paper, state-of-the-art on the development of ultrasonic oil production devices for Enhanced Oil Recovery in China is introduced. The purpose of this paper is to provide a reference for the development of high-power ultrasonic oil extraction equipment and its promotion in tertiary oil recovery technology.     

Transducer line-arrays in the high-frequency range

The transducer array theory developed in the field of underwater acoustics has been used for the design and construction of ultrasonic arrays in the frequency range 600–800 kHz. With these transducers it is possible to scan the acoustic beam electronically and to make the scanning process much faster and less expensive than with a mechanical system. The results show that even higher working frequencies and wider scanning angles can be obtained by developing the technology further.     

The development of recent high-power ultrasonic transducers for Near-well ultrasonic processing technology

With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology.With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology     

超声波流量计在飞机燃油流量测试中的应用研究

燃油系统输油流量测试是飞机燃油系统地面模拟试验的一项重要内容;由于试验油箱内部的各管路与真实飞机油箱管路的布置是一致的,不适合在油箱内的狭小空间安装涡轮流量计,并且会破坏管路流阻特性;由于使用传统油箱油量标定的方法进行输油流量测量耗时耗力,所以需要采用一种新的技术或测量方法来完成油箱输油流量的测量;超声波流量计体积小,不会破坏输油管路流阻特性,防爆等级也符合试验要求;对超声波流量计在浸油状态下测试进行可行性分析,将超声波流量计在飞机燃油系统试验中实现创新性应用;通过试验证明了超声波流量计在飞机燃油流量测试中发挥了重要作用,并且首次将超声波流量计应用到飞机试验油箱内部输油管路的流量测试中,这对飞机其他系统的流量测试和飞机机上排故试验起到了重要作用。     

空间运输航天器故障诊断系统架构研究

故障诊断技术不仅是提高空间运输航天器的安全性和可靠性的重要手段,而且可以节约航天器整个寿命周期的运行维护成本,因此研究航天器故障诊断技术,特别是处理紧急故障的在轨故障检测和诊断技术是非常必要的。在分析国外航天器故障诊断系统发展趋势的基础上,提出了基于天地一体化设计思想的空间运输航天器故障诊断系统架构,阐明了设计原则,以及具体功能需求。介绍了在轨故障诊断系统和地面故障诊断系统,提出了地面故障诊断系统软件的组件模型构成。地面系统对航天器在轨故障诊断有较强的辅助作用,能有效补充故障分析、诊断、预测、处理能力。给出的系统架构对航天器故障诊断系统研制具有一定的参考价值。