纤维束状滤料在虹吸滤池改造中的应用

过滤面积为4.5m×4.5m的虹吸滤池,原设计处理水量为200t/h。采用纤维束状滤料代替单层石英砂滤料进行改造,并增加多孔板配水系统和空气反冲洗,使得单间滤池的处理水量达到400t/h,反洗水量由138.2t降为87.5t,反洗时间由11min降为7min。     

In Situ Rheo-NMR Measurements of Solid Fat Content

The properties of crystallized fats depend on their solid fat content (SFC) and their fractal structures. The SFC and the structures are dramatically affected during crystallization under shear flow. A mini-Couette cell was developed to crystallize fat samples under shear. The cell was tested with blends of canola stearin (CS) in canola oil (CO) in a 20-MHz NMR spectrometer. The blends were placed in the cell, melted at 80 °C, and then crystallized under different shear rates (58–460 s⁻¹) at 40 °C inside the spectrometer for 4 h. Time averaged NMR free induction decay (FID) curves were captured at 20 s intervals. SFC values were calculated using parameters determined by a calibration procedure. The SFC values determined by the direct method with and without the shaft of the Couette device were reasonably close. Similar results were observed with and without shear in the Couette device. The FID curves did not show a significant difference either. Therefore this system is accurate for in-situ time-resolved determination of SFC under shear flow. Furthermore, a combination of the direct and the indirect methods was successfully used to estimate the temperature increase due to viscous heating. The system developed will help in understanding the effects of shear flow on SFC of nanostructured lipid multicomponent systems. This will permit the optimization of the manufacturing processes.     

Design and Optimization of Fibrous Filter Media Using Lifetime Multipass Simulations

The goal of this study was to optimize fibrous filter media by increasing the dust holding capacity (DHC) while maintaining the β ratio and initial pressure drop of the filter media. The key was the use of microstructure models to optimize the filter media. The microstructure of three different variations of a filter media for oil filtration was modeled by using the FiberGeo module of the GeoDict® software package. It was found that by optimizing the fiber volume distribution over the height of the filter media, higher DHC values could be achieved while keeping the pressure drop considerably low. This confirms the hypothesis that the macroscopic properties of the filter element can be improved by modifying the microstructure of the filter media.     

Force Curve Measurements with the AFM: Application to the In Situ Determination of Grafted Silicon-Wafer Surface Energies

The atomic force microscope (AFM) can be used to perform surface force measurements in the quasi-static mode (cantilever is not oscillating) to investigate nanoscale surface properties. Nevertheless, there is still a lack of literature proposing a complete systematic and rigorous experimental procedure that enables one to obtain reproducible and significant quantitative data. This article focuses on the fundamental experimental difficulties arising when making force curve measurements with the AFM in air. On the basis of this AFM calibration procedure, quantitative assessment values were used to determine, in situ, SAM (or Self Assembled Monolayer)-tip thermodynamic work of adhesion at a local scale, which have been found to be in good agreement with quoted values. Finally, determination of surface energies of functionalised silicon wafers (as received, CH₃, OH functionalised silicon wafers) with the AFM (at a local scale) is also proposed and compared with the values obtained by wettability (at a macroscopic scale). In particular, the effect of the capillary forces is discussed.     

Force Curve Measurements with the AFM: Application to the In Situ Determination of Grafted Silicon-Wafer Surface Energies

The atomic force microscope (AFM) can be used to perform surface force measurements in the quasi-static mode (cantilever is not oscillating) to investigate nanoscale surface properties. Nevertheless, there is still a lack of literature proposing a complete systematic and rigorous experimental procedure that enables one to obtain reproducible and significant quantitative data. This article focuses on the fundamental experimental difficulties arising when making force curve measurements with the AFM in air. On the basis of this AFM calibration procedure, quantitative assessment values were used to determine, in situ, SAM (or Self Assembled Monolayer)-tip thermodynamic work of adhesion at a local scale, which have been found to be in good agreement with quoted values. Finally, determination of surface energies of functionalised silicon wafers (as received, CH₃, OH functionalised silicon wafers) with the AFM (at a local scale) is also proposed and compared with the values obtained by wettability (at a macroscopic scale). In particular, the effect of the capillary forces is discussed.     

Data Preprocessing of In Situ Laser‐Backscattering Measurements

In situ measurement techniques are promising tools to aid process development. However, they also pose new challenges in evaluating large amounts of recorded data. A new procedure for in situ laser‐backscattering devices has been developed that allows transformation of the raw recorded data, a chord length distribution, into a format suitable for population balance modeling. Emphasis is thereby laid on the influence of the suspension density on the measured data. Experimental data are recorded using a batch laboratory crystallizer equipped with an in situ 3D‐ORM laser backscattering device and an ultrasound probe. The new proposed five‐step procedure for data preprocessing is based on several independently developed tools from literature and is exemplarily illustrated with results on the crystallization of ascorbic acid. The proposed method is a step forward to use in situ laser‐backscattering devices also for quantitative purposes.     

In Situ Measurements of Bridged Crack Interfaces in the Scanning Electron Microscope

A device for in situ SEM examination of crack propagation during loading of compact tension specimens is described, with a specific demonstration on an alumina ceramic. The device facilitates direct qualitative observations of the inception and subsequent frictional pullout of grain-localized bridges at the crack interface. Quantitative data on the bridging mechanism are obtained from measurements of the crack-opening displacements behind the crack tip. The crack profile is found to be closer to linear than parabolic at the bridged interface. Deconvolution of these crack-opening data allow for an evaluation of the closure tractions operative at the crack walls within the bridging zone, and thence the R -curve.     

Scalable Numerical Tools for Flow and Pressure Drop Computation in Fibrous Filter Media

The prediction of flow behavior and pressure drop in fibrous filter media is challenging due to the complexity of the nonuniform fiber structure. Numerical calculation tools can considerably contribute to pressure drop determination for inhomogeneous filter structures. A numerical solution approach based on the finite element method to simulate 2D and 3D filter structures is considered. As numerical examples, computer designed homogeneous and inhomogeneous 2D cases where the numerical approach is validated by analytical models are investigated. Furthermore, the capability of the numerical method to simulate real 3D structures corresponding to more than 25 million degrees of freedom of the related algebraic system is demonstrated. The large systems involved require the use of dedicated techniques related to high performance computing.     

In Situ Tensile Measurements of Single Fibers by Scanning Electron Microscopy

A newly developed tensile module allows tensile experiments of single fibers to be carried out under visual observation in the scanning electron microscope. This allows correlation of measured data with observed changes in the microstructure, such as surface irregularities and crack formation. With point heating, the thermal behavior of the fibers may be studied up to 2500°C. The results are presented with tensile elongation recordings and micrograph sequences of the structural changes. Carbon fibers with and without an aluminum coating were selected as testing specimens.     

Supercritical Antisolvent Particle Precipitation: In Situ Optical Investigations

The manner in which the presence of a solute can affect the mixing behavior of a solute, solvent and antisolvent in a supercritical antisolvent (SAS) micronization process is demonstrated. The mixing behavior was analyzed by applying a two‐dimensional (2D) Raman scattering technique. Mole fraction and partial density distributions were measured for the CO₂ antisolvent. The results originating from the optical investigations were correlated with the particle results. The experiments cover the variation of the solute concentration at fixed operating conditions of 10 MPa and 40 °C.     

Determination of the Nanoparticle Size Distribution in Media by Turbidimetric Measurements

For incorporation of nanoparticles into matrices, it is necessary to control the particle size distribution during processing. In this paper, a turbidimetric method was applied that uses spectroscopic data to determine the nanoparticle size distribution and, consequently, to control the material properties with a non‐contact measurement method. This method is based on the scattering and absorption of light by the particles. Unlike conventional turbidimetric methods, this method uses not only a few wavelengths but a whole spectral range for evaluation. To determine the distribution parameters, a nonlinear numerical least squares fit routine was established. It was validated by comparing data of water‐silica nanosuspensions with the results from the sedimentation method. The results show that this method is an accurate and easy‐to‐use analysis instrument for the characterization of nanosuspensions, emulsions, and aerosols.     

In Situ Measurements of Frictional Bridging Stresses in Alumina Using Fluorescence Spectroscopy

Fracture of a large-grained alumina polycrystal has been examined in situ by optical microscopy. Concurrently, local bridging stresses, as generated by friction or tension of unbroken ligaments in the wake of the crack path, were measured by piezospectroscopy. Stress measurements were performed both at fixed sites as a function of the external load and at a fixed external load along the crack profile. Frictional stresses were similar/congruent50 MPa, while unbroken ligaments between the crack faces were found to support tensile stresses up to similar/congruent100 MPa. The maximum bridging stress was dictated by the weak (intrinsic) interface bonding of the polycrystal. Average bridging stresses, either theoretically calculated from R -curve data or experimentally measured by piezospectroscopy on frictional/bridging sites, were similar. Such a circumstance enables us to explain the fracture behavior of polycrystalline alumina by considering crack-wake shielding as the main micromechanism contributing to toughening.     

Use of Ambient Aerosols for Measuring Filter Efficiencies

For the evaluation of high-efficiency air filters, it is possible to dispense with aerosol generators and instead use ambient air as a test aerosol, since it contains large numbers of particles up to 0.5 μm. Some instances of such use are described.     

Study of the Sintering of Nanosized Titania Agglomerates in Flames Using In Situ Light Scattering Measurements

ABSTRACT

A premixed flame aerosol reactor was used to produce titania particles by oxidation of titanium isopropoxide vapor. The growth, aggregation of particles, and the agglomerate structure were determined as a function of height in the flame using in situ light scattering and transmission electron microscopy (TEM) measurements. A methodology to determine the sintering characteristic time using light scattering data was established. The light scattering data provided the evolution of the fractal dimension which was then related to the normalized surface area change using a computer simulation. The sintering equation was redeveloped in terms of the normalized surface area, thus not having to account for coagulation effects. Experimental results indicate that isolated titania particles were observed at the high temperatures due to fast sintering. An agglomerate was obtained at downstream locations with an associated change in fractal dimension due to sintering.     

In Situ Ultrasonic Measurements as a Tool to Characterize the Stages of the Zeolite A Crystallization Process

Zeolite A (LTA) was synthesized at 80 °C under hydrothermal conditions from a gel with the molar composition of 2.5 Na₂O : 2 SiO₂ : Al₂O₃ : 80 H₂O. In the present study, we report the use of home-made ultrasound devices as a real-time, in situ diagnostic tool for monitoring the progress of zeolite formation. In addition, the specific aim of this study was to show that the measured ultrasound parameters – ultrasonic (US) velocity and attenuation – simultaneously provide independent information about the changes in the liquid and solid phase, respectively, during the crystallization process. Both views are necessary for extracting kinetic data about the zeolite crystallization processes and allow elucidating the different stages of zeolite LTA formation process. The obtained in situ US data were compared with conventional ex situ powder X-ray diffraction measurements following the formation of zeolite LTA from dense gels. The results demonstrate that a good correlation exists between the crystallization progress of zeolite LTA in terms of crystallinity changes and the ultrasonic attenuation and velocity.     

In Situ Determination of the Physical State of Biological Samples during Freeze Drying

The proceeding change of water content in a freeze-drying process, as well as the physical state of cell–sugar suspensions with Lactobacillus paracasei ssp. paracasei, was monitored by means of an in situ weighing system. Due to the pressure and temperature variations in the drying chamber, the weighing system was found to be influenced. This deviation of the weighing system was quantified by means of drying simulations with drying-inert Teflon dummies. This quantified deviation could be used for correction of the following freeze-drying processes. The applicability of this correction method was verified by drying model sugar solutions with known dry matter. Taking the quantified drift of the balance into account, the measured water contents for the model solution were proved to deviate less than 5% from the actual value. Finally, this verified correction method was applied to freeze drying of cell–sugar suspensions. As a result, the drying course of the cell–sugar samples could be depicted in the appropriate state diagram. Thus, the weighing system could be used to monitor the state transitions, which the bacterial suspension experienced during freeze drying, and qualified for specific investigations on the glassy state during freeze drying.     

A New Experimental Approach for In Situ Damage Assessment in Fibrous Ceramic Matrix Composites at High Temperature

High‐temperature applications of ceramic matrix composites necessitate a rigorous understanding of the fracture and damage mechanisms that occur under thermomechanical loading, requiring the development of advanced small‐scale characterization approaches. In this work, fiber‐reinforced SiC/SiC tensile specimens were loaded in a scanning electron microscope at 800°C, and full‐field deformation maps at the constituent length scale were generated using digital image correlation (DIC). A colloidal system containing mechanically milled titanium nanopowder, bicine, and water was developed for use as a DIC tracking pattern that is stable at 795°C. The resultant full‐field strain maps provide a constituent level characterization of damage evolution from crack initiation through final fracture. An analysis of strain along fiber lengths indicated that fiber mean strain and standard deviation reached a minimum at fiber fracture. In addition, multiple matrix cracks in the process zone ahead of a notch/crack tip were apparent and could falsely appear as a continuous region of high strain in DIC fields. Relatively large displacement (strain) error was attributed to noise and bias at these small length scales and small strain values, and approaches for mitigating this error are discussed.     

EX Situ和In Situ Characterization辨析

前缀词“in situ”和“ex situ”在耐火材料的科技文献中频现。二者都具泛义，在许多情况下可用，弄清其确切含义并贴切地译成汉语十分必要。本文对In Situ和Ex Situ Characterization的含义及其在不同场合的应用作了分析。在表征状态时，in situ和ex situ表达了“原位”和“移位”的不同，互为反义词。用于仪器分析方面，前者表示对被测物在真实环境中的多项同步分析，也表示单项目的连续分析，其连续的意义不可忽视；而后者则指在非原始的、非综合的条件下分别进行的检测，包括用前检测、模拟试验和用后残衬分析。可把在实际正在发生中的、连续的、综合的观察和分析，统称为In Situ Characterization；而用前的检测、模拟试验和用后残衬分析，可统称为Ex Situ Characterization。如何译成中文，要弄清具体的背景和含义，无需硬译。     

纤维过滤器内部微观结构可视化的研究进展

对纤维过滤器内部微观结构可视化方法的研究进展进行了综述,结果表明国内外在过滤器内部微观结构可视化方面主要采用:扫描电镜(scanning electron microscopy,SEM)、X-射线照相术(X-ray computerized tomography)及核磁共振成像法(magnetic resonance imaging,MRI)。通过比较后认为应用非侵入式成像技术-MRI方法来预测纤维过滤器的内部微观结构可以获得较为真实的过滤器内部结构。在此基础上分析了基于MRI方法并利用计算流体力学(CFD)技术研究过滤器内气固两相流动的可行性。