超声波协同铁粉降解水中2,4-二氯酚的研究

采用超声波/铁粉协同降解水中2,4-二氯酚。考察了初始浓度、超声功率、铁粉投加量以及pH对降解效率的影响,并初步探讨了超声波/铁粉协同降解2,4-二氯酚的动力学规律。结果表明,超声波与铁粉对2,4-二氯酚的降解具有明显的协同效应。降解效率随超声功率和铁粉投加量的增大而增大,随初始浓度的增大而减小。pH对2,4-二氯酚的降解有显著影响,在pH为4时,降解效率最高。超声波/铁对2,4-二氯酚的协同降解符合一级反应动力学规律,降解速率常数为1.52×10-2min-1,与铁粉单独作用和超声单独作用相比,分别提高了约5倍和13倍。     

Measurement of longitudinal distribution of solids holdup in a three-phase fluidized bed by ultrasonic technique

A method of measurement of solids holdup in a three-phase reactor by analyzing the shape and the phase lag or lead of an ultrasonic wave has been proposed. The solids holdup in a solids-dilute three-phase fluidized bed could be measured without being affected by the presence of gas bubbles. The experimental values of solids axial dispersivity measured by the ultrasonic technique are in reasonable agreement with an empirical correlation of previous data obtained by other methods. The possibility of the application of the ultrasonic technique to the measurement of solids holdup in a three-phase fluidized bed has been suggested.     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

Molar volume and ultrasonic studies of europium soaps in mixed organic solvents

The ultrasonic velocity and density measurements of europium soaps in a mixture of benzene and methanol (3:2, vol/vol) were used to evaluate various acoustic parameters and molar volume and to determine the critical micelle concentration. The results showed that the ultrasonic velocity, specific acoustic impedance, molar sound velocity, and molar compressibility increase, and intermolecular free length, adiabatic Compressibility, and relative association decrease with increasing concentration and chainlength of the soap. The results were interpreted in terms of soap-solvent interaction.     

Ultrasound as a Tool to Synthesize Nano-Sized Silica–Alumina Catalysts with Controlled Mesoporous Distribution by a Novel Sol–Gel Process

A novel sol–gel process is used to synthesize mesoporous silica–alumina catalysts with controlled pore size distribution without using templates or pore-regulating agents. The nitrogen sorption analysis shows that the synthesized materials have high specific surface area in the range 587–692 m²/g and similar mesoporous distribution within 2–11 nm. Ultrasound is applied to prepare precursor silica–alumina sol with narrow particle diameter distribution. By calculation, it is found that ultrasonic treatment is able to provide 22.94 kJ/mol energy, which is just in accordance with the weak bond's bonding energy. Based on the calculation result, it is proposed that the role of ultrasonic treatment followed by acid peptization is to provide energy to break down the weak bonds. After gelation, the regular and close packing of similar-sized sol particles is capable of formation of controlled-sized interstices which are the precursors of mesopores. Solid-state ²⁷Al MAS NMR and TEM are used to characterize the samples' structure and particle morphology. They show that most of the aluminum is located in the tetrahedral position in the present materials. According to TEM results, it is shown that the synthesized materials have spherical particles with size of about 15 nm.     

<Emphasis Type="Italic">In situ</Emphasis> monitoring of solid fat content by means of pulsed nuclear magnetic resonance spectrometry and ultrasonics

An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC. TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r ²>0.9) in a linear fashion (v=2.601 SFC+1433.0).     

高强混凝土受火后力学性能变化规律的研究

对受火后的混凝土试件进行了抗压强度、抗折强度和劈裂抗拉强度试验,讨论了温度、强度等级、试件尺寸、含水量对其高温后力学性能的影响。研究表明,受火后,抗折强度较抗压强度下降更快;高强度的混凝土在600℃前抗压强度下降不多;大尺寸混凝土试件较小尺寸混凝土试件的残余抗压强度下降慢;混凝土试件的含水率越高,相对残余抗压强度越低。采用超声波速度法和质量损失法对火灾高温后混凝土内部结构的变化进行了探讨。     

Ultrasonic oscillations effect on rheological and processing properties of metallocene‐catalyzed linear low density polyethylene

The effects of ultrasonic oscillations and die materials on die pressure, productivity of extrusion, melt viscosity of metallocene‐catalyzed linear low density polyethylene (mLLDPE), as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. Die materials used in our experiment included steel, brass, and polytetrafluoroethylene (PTFE)_. The experimental results showed that ultrasonic oscillations as well as die materials have great influence on the rheological and processing behavior of mLLDPE. Ultrasonic oscillations can greatly increase the productivity of mLLDPE melt extruded through different dies, and can decrease the die pressure and the melt viscosity of mLLDPE. Compared with steel or brass die, mLLDPE melt extruded through PTFE die is more sensitive to ultrasonic oscillations. A possible mechanism for the improved processability of mLLDPE is proposed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1873–1878, 2003     

超声波测距的模糊控制泊车系统模型设计

设计了一种基于超声波测距的自动泊车系统模型。首先对小车运动模型进行分析,结合实际设计垂直、平行、斜行三种泊车模糊控制器,并且在Matlab的Simulink中分别进行仿真验证。采用超声波测距技术、视频采集技术等来获取周围环境数据,按照实际车辆和车库的大小,通过等比例缩放设计小车模型和车库模型,并把验证通过的模糊控制器转换为C代码,嵌入到飞思卡尔K60主控制板中进行自动泊车可行性测试。经测试,当模型车的航向角在-32°~+32°范围内时,实现了模型车在0.92倍标准大小模型车库内的自主泊车。     

新型非侵入式超声物位检测方法研究

在石化行业,存在大量装载颗粒物料的反应器和容器,其料位的实时准确检测对于生产过程的控制和优化具有非常重要的作用.本文利用超声辐射阻尼原理,揭示了料仓中物料料位的高低与固体介质表面传播的超声振动吸收的定量关系,建立了颗粒状物料料位高度的关联公式.该公式可以定量地描述物料位高度与超声振动能量的衰减、颗粒物理性质和振动传递介质的关系,具有较高的精度.同时,通过成纵向排列的一系列接收探头所接收到的脉冲超声波能量的峰能量比,可以确定出储罐内液位的高度,其检测精度与接收探头的数量成正比.研究结果表明,无论是颗粒料位还是液体料位,都能利用基于超声辐射阻尼原理研制的浙江大学联合化学反应工程研究所UGAS-05声检测系统实现料位的实时在线检测.