Dynamic response of a hydraulic servo-valve torque motor with magnetic fluids

As magnetic fluids (MF) show higher saturation magnetization and larger viscosity when exposed to a magnetic field, large damping forces or resistance will be exerted on the armature of a hydraulic servo-valve torque motor by magnetic fluids if they are filled into the working gaps of the motor. This paper focuses on the application of magnetic fluids in a hydraulic servo-valve torque motor, especially the influence of magnetic fluids on the dynamic response of the motor. After introducing the working principle of the torque motor with magnetic fluids, the dynamic mathematical models of the torque motor and magnetic fluids are presented. The torque working on the armature introduced by magnetic fluids is analyzed. In order to study the influence of magnetic fluids, dynamic response of the torque motor is simulated and tested when magnetic fluids are applied or not in the motor. Simulation and experimental results show an obvious influence of magnetic fluids on the dynamic response of the hydraulic servo-valve torque motor.     

Light-guiding effect in a two-fluid model of laser angioplasty

Mixing and optical characteristics of blood and optical fluid, utilized in laser angioplasty, are investigated with a two-fluid model. Transport equations are solved for the zone-averaged variables of each fluid with allowance for momentum transport at the interface. The predicted volume fractions of the fluids are used as weight functions to calculate the mixture refractive index. A set of light rays are traced through the fluids to the plaque, utilizing the mixture refractive index. The results indicate significant effect of flow characteristics on the focusing of the rays     

Characterization of the electrochemical behavior of gastrointestinal fluids using a multielectrode sensor probe

A characterization of gastrointestinal fluids has been performed by means of an electrochemical sensor that has potential for clinical in vivo and in vitro monitoring applications. The sensor comprised a three-electrode cell with a counter, reference, and four working electrodes, Au, Pt, Ir, and Rh. Cyclic voltammetry was used to obtain chemical information from faecal water (in vitro) and gut model (in vivo) fluids. Stable voltammetric responses were obtained for both fluids at these noble metal working electrodes. The responses differed in shape that demonstrated the discrimination capability and the potential for practical use as a tool for gastrointestinal fluid investigation. The analysis of the stability profiles in faecal water over a 14-h duration has indicated a possible adsorption mechanism with the formation of a biolayer on the sensor surface. The stability in gut model fluids over a 42-h duration has demonstrated a more stable profile, but the mechanisms involved are more complicated to determine.     

Index matching fluids for long wavelength (1.2?1.6 ?m) fibre-optic applications

Halocarbon fluids (FXCCF2)n, where X = Cl or Br have been used to index-match silica in the 800?2000 nm region. These fluids, unlike silicones or hydrocarbon fluids, are free of CH and OH absorption, and are resistant to hydrolysis and moisture absorption.     

硬脆性材料线切割切削液的组成和发展

综述了国内外太阳能光伏产业及半导体等高精端电子产业中硬脆性材料线切削液的发展、分类和应用.归纳总结了国内外近年来切削液的使用量,对2008年的市场需求进行了预测,重点分析综述了国内外水性切削液产品组成、配方的研究进程及切削液产品对线切割工艺过程、晶片质量的影响,并对国内线切削液今后的发展提出了建议.     

底部填充工艺的瞬时温度环境管理

微电子组装的大部份工艺开发都要求将元件做到更小,以便在尺寸日益缩小的便携式设备上实现更多功能。阐述了大元件的底部填充,即一侧的尺寸超过15mm,底部填充的胶量介于30～50mg。大尺寸晶元的制造工艺要求比现有生产线更大的产能,这就给底部填充点胶带来更大的挑战。大元件的产能超过3000个/h时,需要点胶机点出非常多的胶水。如此多的胶水在出胶前通过点胶阀,这将会带来加热的问题-某些工艺要求出胶前胶水必须要加热。这会对胶点尺寸有影响,因为随着温度的变化,底部填充的胶水黏度也会随之变化,从而轻微影响点出的胶量。从而将影响晶元相邻的“非沾染区”。稳定的温度是点胶稳定性的保证,并且能帮助胶水流进晶元下方同时也有助胶水分离从而更容易喷射出来。从研究中可以观察到：系统温度环境（点胶机内部）对点胶的胶水质量有影响。     

Magnetic Fluids: Fabrication,Magnetic Properties,and Organization of Nanocrystals

In this paper we outline different ways to make magnetic fluids from colloidal self‐assemblies (normal and reverse micelles) and describe the preparation of both ferrite nanocrystals with various compositions and cobalt metal nanocrystals. The general magnetic behaviors are described but it is found that these are not applicable to the whole variety of ferrites produced. Ferrite and cobalt magnetic fluids are organized in 3D superlattices to form various mesoscopic structures. Within a number of limitations, the magnetic properties of both the above nanocrystals and these fluids have been determined and described.     

Low-Temperature Passivation of Amorphous-Silicon Thin-Film Transistors With Supercritical Fluids

In this letter, supercritical CO₂ (SCCO₂) fluids technology is employed for the first time to effectively passivate the defect states in hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) at low temperature (150degC ). With the high transport and diffusion properties of fluids, it is proposed to act as a transporter in delivering the molecules into the amorphous-silicon film and repairing defect states by the molecules. In addition, the propyl alcohol is used as the surfactant between nonpolar-SCCO₂ fluids and polar-H₂O molecules for mingling H₂O molecules uniformly with the SCCO₂ fluids. After the treatment of SCCO₂ fluids mixed with water and propyl alcohol, the a-Si:H TFT exhibited superior transfer characteristics and lower threshold voltage. The improvement in electrical characteristics could be verified by the significant reduction of density of states in the mobility gap of amorphous-silicon.     

MR fluid,foam and elastomer devices

Magnetorheological (MR) fluids, foams and elastomers comprise a class of smart materials whose rheological properties may be controlled by the application of an external magnetic field. MR fluids are liquids whose flow or shear properties are easily controlled to enable a variety of unique torque transfer or vibration control devices. MR foams, in which the controllable fluid is contained in an absorptive matrix, provide a convenient way of realizing the benefits of MR fluids in highly cost sensitive applications. MR elastomers are solid, rubber-like materials whose stiffness may be controlled to provide tunable or adjustable mounts and suspension devices.     

Modulation of near-millimetre-wavelength radiation by magnetic fluids

The results of some measurements on amplitude modulation of 94, 100 and 110 GHz radiation by a magneto-optical effect in a number of magnetic fluids are described. Modulation at frequencies up to 0.25 MHz has been observed, but this may not represent the intrinsic high-frequency cutoff of the effect. The effects of altering both the composition and the concentration of the magnetic fluid are described.     

氟氯系列折射率匹配液的研究和应用

研究了氟氯系列折射率匹配液,测量并考核了其各项性能。结果证明该系列和KD~*P电光晶体能达到比氟碳系列更精细的匹配。降低了晶体界面的反射达20多倍,透过率增加10％以上,在冰洲石棱镜表面的匹配也取得满意的效果。     

Oblique-tip fiber-optic sensors for multiphase fluid discrimination

This paper describes several novel designs of fiberoptic sensor made from standard silica fibers with plane oblique facets polished at the fiber tip, and various surface treatments. All use the phenomenon of total internal reflection (TIR) to distinguish drops, bubbles or other moieties of immiscible fluids in a multiphase flow, on the basis of contrast in refractive index. Surface treatments for control of wettability can be critical to some of the conceptions. Depending on the geometry chosen, sensors with quasibinary outputs may be made to distinguish various pairs of immiscible fluids (liquid/gas or oil/“not-oil”). Sensor pairs may then be used for discrimination of three mutually immiscible phases (oil, water, gas) in complex flows. Example outputs from prototype sensors in laboratory test flows are shown     

微气泡执行器强化微混合的实验研究

微尺度流动的雷诺数(Re)比较低,其混合主要通过扩散来完成,因此需要较长的距离与时间才能混合均匀。为实现微尺度低Re数流体的快速均匀混合,以甲醇及染色甲醇为工质,采用脉冲电压激励微铂膜产生可控气泡,并以气泡周期性胀缩产生的脉冲压力为动力源,研究脉冲压力横向扰动产生的混沌流对微通道内流动混合的影响。结果表明:脉冲压力横向作用使流体的交界面产生了强烈的卷曲拉伸,有效地强化了混合,该微混合器能够在毫米级混合长度及毫秒级混合时间内快速均匀混合,脉冲频率越高,混合效果越好。本研究结果为解决微尺度下低Re数流动混合难题提供了一种有效的崭新手段。     

Polymeric Confonnal Coatings for Implantable Electronic Devices

Long-term implantable devices such as cardiac pacemakers are protected from corrosive tissue fluids by means of a metallic, hermetically sealed enclosure. When the electronic circuitry contacts infiltrating tissue fluids due to a corrosive breach in the hermeticity, failure of the device is almost immediate. Polymeric coatings have been investigated to serve as a secondary moisture barrier in this work.     

Hydrofluoroethers as heat-transfer fluids for OLEDs: Operational range, stability, and efficiency improvement

In this work we introduce a simple yet very efficient method of heat dissipation by immersing OLED device into hydrofluoroether (HFE) fluids. It is shown that due to highly fluorous nature of this class of fluids, HFE do not damage organic semiconductors which are comprised in the OLED stack and therefore can be used as encapsulation media. HFE also have high thermal conductivity, low viscosity and can efficiently dissipate the heat by means of natural convection with laminar flow. By employing HFE we were able to significantly improve the OLED operating dynamic range. Lifetimes of OLEDs operating in HFE at high currents can be improved by about a factor of 8. Furthermore, HFE fluid significantly improves the light outcoupling by a factor of 70% due to higher than air refractive index (n = 1.3).     

Hierarchically Nested Channels for Fast Squeezing Interfaces With Reduced Thermal Resistance

We report on a simple method to improve bondline formation kinetics by means of a hierarchical set of channels patterned into one of the surfaces. The channel arrays are used to improve the gap squeezing and cooling of single and multiple flip-chip electronic modules with highly viscous fluids and thermal pastes or greases. They allow a fast formation of thin gaps or bond lines by reducing the pressure gradient in the thermal interface material as it moves in and out of the gap. Models describing the dynamics of Newtonian fluids in these "hierarchically nested channel" interfaces combine squeeze flow and Hagen-Poiseuille theories. Rapid bond-line formation is demonstrated for Newtonian fluids and selected particle-filled pastes. Modeling of particle-laden polymeric pastes includes Bingham and Hershel-Bulkley fluid properties. Bond-line formation and thermal resistance are improved particularly for high-viscosity high-thermal-conductivity interface materials created from higher-volumetric particle loadings or for thermal interface materials with smaller filler-particle diameters     

Artificial Cilia–Bridging the Gap with Nature

Human ingenuity has found a multitude of ways to manipulate fluids across different applications. However, the fundamentals of fluid propulsion change when moving from the macro- to the microscale. Viscous forces dominate inertial forces rendering successful methods at the macroscale ineffective for microscale fluid propulsion. Nature however has found a solution; microscopic active organelles protruding from cells that feature intricate beating patterns: cilia. Cilia succeed in propelling fluids at small dimensions; hence they have served as a source of inspiration for microfluidic applications. Mimicking biological cilia however remains challenging due to their small size and the required kinematic complexity. Recent advances have pushed artificial cilia technology forward, yet discrepancies with natural cilia still exists. This study identifies this gap by analyzing artificial cilia technology and benchmarking them to natural cilia, to pinpoint the remaining design and manufacturing challenges that lay at the basis of the disparity with nature.     

Magnetosonic Waves in a Two-Dimensional Electron Fermi Liquid

Semiconductors - The properties of highly viscous fluids at high frequencies become similar to those of amorphous solids. In particular, the propagation of not only longitudinal acoustic waves...     

军用激光器冷却液的研制

XW1军用固体激光器冷却液适用于重复频率固体激光器.它具有比热大,热传导系数高,对冷却系统无腐蚀作用,适用温度范围(-65℃～99℃)大的优点.该冷却液主要由卤化锂、水组成,并含有阻化剂及提高热传导系数的有机添加剂.     

Lubricant‐Infused Anisotropic Porous Surface Design of Reduced Graphene Oxide Toward Electrically Driven Smart Control of Conductive Droplets' Motion

The study of Nepenthes pitcher plants‐bioinspired anisotropic slippery liquid‐infused porous surfaces (SLIPS) is currently in its infancy. The factors that influence their anisotropic self‐cleaning and electric response of a drop's motion and the mechanism have not been fully elucidated. In order to address these problems, two new types of anisotropic slippery surfaces have been designed by using directional, porous, conductive reduced graphene oxide (rGO) films, and different lubricating fluids (conductive and nonconductive), which are used to study the influencing factors and the mechanism of anisotropic self‐cleaning and electric‐responsive control of a drop's motion. The results demonstrate the anisotropic self‐cleaning property of these two types of SLIPS is closely related to the interaction between liquid drops, lubricating fluids and dirt, and the conductive lubricating fluids filling the rGO porous film can reduce the response voltage of the electrically driven reversible control of a drop's slide. The uniqueness of this research lies in the use of two different lubricating fluids and graphene materials to prepare anisotropic SLIPS, identify the key factors to achieve an electrically driven system. These studies are essential for advancing the application of electronically responsive SLIPS in the fields of liquid directional transportation, microfluidics, microchips, and other related research.