单轴式声悬浮的物理特性

采用边界元方法对单轴式声悬浮过程中的人射声场计算,揭示了样品在声悬浮过程中的受力特性,结果表明,提高声源强度,降低重力水平或者采用密度大声速小的气体介质有利于提高声悬浮能力,另外,采用适当曲率半径和较大截面半径的凹球面反射端能够提高模式4下靠近反射面的一个悬浮位置的悬浮性能。     

ICF靶丸类微球在近场声悬浮系统中的悬浮实验研究

为实现均匀辐照,ICF靶的无接触支撑是关键。提出用近场声悬浮对ICF靶进行无接触支撑,对悬浮ICF靶丸类微球的压电换能器和悬浮系统进行了初步设计,换能器发射端采用了凹球面结构,利用ANSYS软件对发射端的凹球面结构进行了优化。并构建了近场声悬浮测试系统,对不同直径的钢球在不同工作电压下进行了悬浮实验。实验结果表明：当发射端凹球面直径与钢球直径接近或相等时,悬浮效果是最好的,并且用气动的方式可以实现悬浮钢球的非接触驱动。当工作电压为600V时,钢球的悬浮高度为50μm,扰动振幅为3μm,这说明ICF靶近场声悬浮是可行的。     

声悬浮的研究应用进展

声悬浮是一种新型无容器处理技术，悬浮力及悬浮稳定性是声悬浮研究的两个重要方面。本文在查阅大量文献的基础上，阐述了声悬浮的机理，论述了声悬浮技术的研究应用进展，最后讨论了声悬浮技术尚需解决的问题。     

悬浮颗粒物海水及其声吸收

通过对悬浮颗粒物粘滞性声吸收的分析,指出了在悬浮颗粒物海水声传播研究中所需要的悬浮颗粒物参数;经海水中声吸收计算分析,给出了能够对声传播产生影响的悬浮颗粒物参数的范围。为应用于声学研究的悬浮颗粒物海水海洋调查、数据积累及海区划分提供依据。     

超声驻波悬浮特性仿真研究

为了研究驻波悬浮器参数对声悬浮能力大小的影响,使用多物理场有限元仿真软件COMSOL Multiphysics,对驻波声场进行仿真.通过改变谐振腔长度来影响驻波形成条件,得出驻波声压随谐振腔长度的变化关系;在特定超声频率及振幅下,通过控制超声换能器及反射面的尺寸,得到声压随悬浮器尺寸改变的曲线,从而获得最佳悬浮效果所需的模型参数;使用粒子追踪模块,仿真粒子在声场中的悬浮情况,并以可视化方式展示结果,反映出粒子悬浮位置与声压分布的关系.     

指数型旋转辐射体近场声悬浮系统的声场分析

0引言如何产生足够大的悬浮力是近场声悬浮一个关键问题。本文受到聚焦超声悬浮的启示[1、2],将近场声悬浮系统中的圆盘辐射体用指数型旋转辐射体取代,并建立了其有限元二维模型[3],对其进行了理论分析和计算,并对圆盘及指数型旋转辐射体的辐射声压做了一番比较,发现了当使用后者时,声悬浮的悬浮力有一定的提高。     

丙烯酸系二元共聚高吸油性树脂的合成及性能研究

采用悬浮聚合法合成了丙烯酸系二元共聚高吸油性树脂,系统研究了悬浮聚合丙烯酸系二元共聚吸油性树脂中不同单体配比．交联剂用量,反应温度等因素的影响,对吸油性树脂的吸油倍率、保油率以及耐热耐寒性能进行了研究。     

悬浮隧道水下锚索抑振装置试验研究EI北大核心CSCD

悬浮隧道锚索是连接悬浮隧道管体与水下基础的重要构件,其在水流作用下可能会发生涡激振动,导致结构疲劳,影响结构安全。因而,研究悬浮隧道锚索涡激振动的抑制方法,具有重要的理论和现实意义。设计了三种抑振装置:螺旋条纹,控制杆和整流罩,采用试验方法研究了其抑振的有效性和适用性。通过试验发现,随着锚索倾斜角度的减小,三种抑振装置的抑振效果均有不同程度的提高,其中以三螺旋线的抑振效果最好且最稳定;随着来流角度的增大,三螺旋线和整流罩的抑振效果会不同程度的提升,但三控制杆对来流角度变化较为复杂;在多参数综合影响下,三螺旋线的抑振性能最好,推荐使用。     

核壳结构吸水性树脂的制备及性能研究

采用饥饿态半连续加料方法,对反相悬浮聚合制备核壳结构聚丙烯酸钠高吸水性树脂进行了研究。结果表明,该法制备的产品各项性能均优于溶液聚合法和一般反相悬浮聚合法制备的产品。     

透明ABS树脂合成技术研究

采用乳液聚合工艺合成丁苯胶乳(SBL),采用悬浮聚合合成甲基丙烯酸甲酯-苯乙烯-丙烯腈(MSAN)树脂,通过调整SBR上的接枝单体比例,使MBS树脂的折光指数与MSAN树脂匹配,通过熔融共混获得综合性能良好的透明ABS树脂产品.     

Axisymmetric analysis of a tube-type acoustic levitator by a finite element method

A finite element approach was taken for the study of the sound field and positioning force in a tube-type acoustic levitator. An axisymmetric model, where a rigid sphere is suspended on the tube axis, was introduced to model a cylindrical chamber of a levitation tube furnace. Distributions of velocity potential, magnitudes of positioning force, and resonance frequency shifts of the chamber due to the presence of the sphere were numerically estimated in relation to the sphere's position and diameter. Experiments were additionally made to compare with the simulation. The finite element method proved to be a useful tool for analyzing and designing the tube-type levitator.     

用于晶体生长的地基无容器悬浮技术

空间微重力环境下几乎无对流和沉降,可为晶体生长提供一个相对稳定和均一的理想环境,易于得到尺寸较大的高质量单晶。但是,空间结晶实验成功率低,费用昂贵,实验机会受限。因此,研发各种空间微重力环境地基模拟技术具有重要意义。目前可用于晶体生长的地基无容器悬浮技术主要有空气动力悬浮、静电悬浮、电磁悬浮、液体界面悬浮、超声悬浮和磁场悬浮技术等。这些地基模拟技术可实现晶体的无容器悬浮生长,避免器壁对晶体生长的不良影响,提高晶体质量,为解决X射线单晶衍射技术中的瓶颈问题提供新途径,还可为在地基进行结晶动力学和机理研究提供简单易行的方法。从技术原理、优势、缺陷及在结晶(特别是蛋白质结晶)中的应用4个方面对这些技术逐一进行了介绍和评述。重点介绍了液体界面悬浮、超声悬浮和磁场悬浮技术这3种用于蛋白质晶体生长的较为成熟的地基无容器悬浮技术。     

Quantitative investigation of particle formation of a model pharmaceutical formulation using single droplet evaporation experiments and X-ray tomography

The implementation of a particle design platform that can be applied to novel pharmaceutical systems using acoustic levitation (SAL) and X-ray tomography (XRT) is discussed. Acoustic levitation was employed to provide a container-less particle design environment for single droplet evaporation experiments. Dried particles were subject to further visual and quantitative structural analysis using X-ray tomography to assess the three-dimensional volume space. The workflow of the combined SAL-XRT platform has been applied to investigate the impact of increasing HPMC K100LV concentrations on the evaporation, drying and final particle morphology of particles from a model pharmaceutical formulation containing metformin and D-mannitol. The morphology and internal structure of the formulated particles after drying are dominated by a crystalline core of D-mannitol partially suppressed with increasing HPMC K100LV additions. The final structure can be correlated to the observed evaporation kinetics. The characterisation of formulated metformin hydrochloride particles with increasing polymer content demonstrated the importance of an early-stage quantitative assessment of formulation-related particle properties. The ability to study the evolution of solid phase formation and its influence on the final particle morphology can enable the selection of formulation and process parameter that deliver the desired particle structure and consequent performance by design.     

Enzyme kinetics in acoustically levitated droplets of supercooled water: a novel approach to cryoenzymology

The rate of the alkaline phosphatase-catalyzed hydrolysis of 4-methylumbelliferone phosphate was measured in acoustically levitated droplets of aqueous tris (50 mM) at pH 8.5 at 22 +/- 2 degrees C and in supercooled solution at -6 +/- 2 degrees C. At 22 degrees C, the rate of product formation was in excellent agreement with the rate observed in bulk solution in a cuvette, indicating that the acoustic levitation process does not alter the enzyme activity. The rate of the reaction decreased 6-fold in supercooled solution at -6 +/- 2 degrees C. The acoustic levitator apparatus is described in detail.     

Effects of Sample Size on Surface-Tension Measurements of Nickel in Reduced-Gravity Parabolic Flights

Surface tensions of molten metals have been reported in the literature by application of many standard techniques: sessile-drop, maximum bubble pressure, pendant-drop, and capillary-rise methods. Great experimental care must be exercised to ensure the absence of contamination, and containerless techniques based upon the classical theory of oscillations of a liquid drop are being developed for high-precision measurements on reactive alloys. Droplet positioning and heating can be efficiently accomplished by electromagnetic levitation, although additional modes of oscillation can be excited and the fundamental oscillation mode can be shifted to higher frequencies due to asymmetries in droplet shape when experiments are performed in earth-based laboratories. These additional factors associated with 1 g experiments significantly complicate data analysis. An electromagnetic levitator has been developed at Auburn University to test containerless processing methods for characterizing the surface tension of high temperature, reactive melts. Recent oscillating drop experiments with nickel samples utilizing electromagnetic levitation in the low-g environment of NASA's KC-135 research aircraft have shown droplet oscillations in the primary mode and at the fundamental frequency. A series of experiments was performed with droplets covering a range of sizes (i.e., mass), and the largest samples exhibited the largest deviations from Rayleigh's simple theory. The smallest samples exhibited oscillatory behavior consistent with Rayleigh's simple theory. An uncertainty analysis showed that the oscillating-drop technique should provide uncertainties in surface tension of ±0.1 to 2.0percnt; depending upon the uncertainty in the mass of the sample.     

电磁悬浮熔炼系统的结构及其悬浮力的研究

电磁悬浮熔炼技术是伴随着对特种纯净材料的需求以及航天等高新技术中对微重力研究等而产生和发展起来的，因其重要的科学技术地位而受到关注。本文从电磁基本理论从发，对轴对称螺线锥管电磁悬浮熔炼系统的结构进行分析，得到悬浮系统几何参数与悬浮力的关系；对悬浮系统中平衡线圈的结构进行改进，计算结果表明，改进结构具有较大的悬浮力。据此研制的试验系统实现了电磁全悬浮。     

Matrix method for acoustic levitation simulation

A matrix method is presented for simulating acoustic levitators. A typical acoustic levitator consists of an ultrasonic transducer and a reflector. The matrix method is used to determine the potential for acoustic radiation force that acts on a small sphere in the standing wave field produced by the levitator. The method is based on the Rayleigh integral and it takes into account the multiple reflections that occur between the transducer and the reflector. The potential for acoustic radiation force obtained by the matrix method is validated by comparing the matrix method results with those obtained by the finite element method when using an axisymmetric model of a single-axis acoustic levitator. After validation, the method is applied in the simulation of a noncontact manipulation system consisting of two 37.9-kHz Langevin-type transducers and a plane reflector. The manipulation system allows control of the horizontal position of a small levitated sphere from -6 mm to 6 mm, which is done by changing the phase difference between the two transducers. The horizontal position of the sphere predicted by the matrix method agrees with the horizontal positions measured experimentally with a charge-coupled device camera. The main advantage of the matrix method is that it allows simulation of non-symmetric acoustic levitators without requiring much computational effort.     

微型静电悬浮Z向加速度计的计算机模拟

本工作针对一种新型的电容式力平衡加速度计－微型静电悬浮Ｚ向加速度进行了计算机模拟。模拟中的Ｚ向加速度计拟采用微机械加工技术在硅片上制作，利用静电悬浮原理平衡质量块，感应加速度并输出信号。计算机模拟分析了加速度计的悬浮特性，稳定特性，响应特性。对Ｃ－Ｆ转换电路的输出特性也进行了分析，该电路可用ＣＭＯＳ工艺集成在加速度传感器的周围。模拟结果表明该加速度计的悬浮特性，稳定特性，响应特性。对Ｃ－Ｆ转换电路