Permeation through a bed on a vibrating medium: theory and experimental results

A dead-end filtration set-up with a vertically vibrated medium is used to study cake permeation. A key feature of these experiments is that a sudden increase in permeability at a certain critical vibration amplitude takes place, when the static loading is light. A theory to explain this phenomenon is put forward in terms of a relation to local fluidization near the medium, thus returning the clogged septum resistance to virtually its unclogged value. The fluidization is due to a particle stress induced by the vibration of the particle fluid mixture near the medium. This stress can be large enough to counteract the compressive stress that is caused by gravity and drag due to the fluid flow in the set-up.Estimates for the particle stresses are obtained; these are proportional to the amplitude decay inverse length λ. The latter is derived from the analysis of a vibrated particle-fluid mixture that is in a state of fluidization. It is argued that only in this state will the value of λ be large enough to generate the required particle stress. A much smaller value for λ is obtained when the particles in the medium make enduring contacts.The theory predicts a frequency dependence for the turnover point in the permeability according to the root of the applied frequency. This theoretical result is confirmed by the experiments. The theory also predicts that when the decay is too steep, so that the vibration amplitude vanishes at a distance of less than a particle diameter, no fluidization will occur. This is found to be true for larger cake masses.     

Pollutant destruction in a reverse-flow chromatographic reactor

A reverse-flow chromatographic reactor (RFCR) is a packed reactor in which the flow direction is reversed periodically and in which one of the reactants is strongly adsorbed on the catalyst. We study the performance of a RFCR used to destruct a pollutant A by a reaction with a reactant B, the emission level of which is subject to even stricter restrictions. Due to safety considerations, this reactant B is introduced in the center of the reactor. The RFCR operation enables a reduction of the regulated effluent products well below the minimum attainable under a steady-state operation of the same packed-bed reactor. Moreover, it can respond effectively to any perturbations in the pollutant feed rate and/or concentration. When the environmental regulations on the emission of B are stricter than those of A, it is often advantageous to feed slightly less B than the amount needed for complete conversion of A. We present a methodology for finding the operating conditions that lead to the minimal level of weighted emission of both A and B. A continuous feed of the reactant B is superior to operation in which the same amount of B is fed during each semi-cycle but in a non-continuous fashion.     

Harmonic analysis for identification of nonlinearities in impedance spectroscopy

Though impedance is only defined for linear systems, impedance spectroscopy is also successfully applied to nonlinear systems such as fuel cells and batteries. The influence of nonlinearities on measurement results in impedance spectroscopy is therefore discussed on a theoretical and simulative basis.The basis is a simplified Randles model of an electrochemical cell, on which a simulated impedance spectroscopy in galvanostatic mode is performed. For the investigation the focus is on the Butler-Vollmer equation in order to describe the nonlinearity. Furthermore, a linear model for comparison is used, in which the Butler-Volmer nonlinearity is replaced by a linear resistor to show the differences in impedance measurement.In order to find a correlation, also the occurring harmonics are observed. The results are discussed and several methods are suggested for maintaining a quasi-linear impedance measurement by controlling the amplitude of the excitation signal.     

Development of a novel electrochemical immuno-assay using a screen printed electrode for the determination of secretory immunoglobulin A in human sweat

This paper reports on the steps involved in the development of a novel electrochemical immunoassay for secretory immunoglobulin A (sIgA) determinations in human sweat. This novel immunoassay involves an initial step whereby sweat sIgA is adsorbed onto a polyvinylidene fluoride (PVDF) membrane (sweat patch). Following a wash step, a solution containing bovine serum albumin (BSA) is used to block any sites at which non-specific binding might occur. After a second wash step, the PVDF sweat patch is transferred to a second tube to which is added diluent and anti-sIgA antibody conjugated to horseradish peroxidase (HRP). Following an incubation step, an aliquot of supernatant containing unbound antibody is transferred to a well in a 96 well plate format which had been previously coated with sIgA. After a second incubation step and wash step, 3,3′,5,5′-tetramethylbenzidine (TMB) is added to the same well and left to undergo enzymatic oxidation. Finally a screen-printed carbon electrode (SPCE) is inserted into the well and any oxidised TMB is detected by chronoamperometry using an applied potential of +50 mV. The resulting reduction current is then referred to a calibration plot to deduce the unknown sIgA concentration. The optimisation of the steps involved in this assay is described in detail. Some preliminary data is presented on sweat sIgA levels collected from human volunteers who had undergone a controlled exercise regime on a bicycle (Ergociser). To our knowledge this is the first report where a sweat patch and a SPCE have been successfully incorporated into an immunoassay for sIgA.     

Chromatic interior environments for the elderly: A literature review

The impact of the physical environment on individuals has arisen as a growing body of research in population wellbeing. Yet, most of studies in this area do not focus on elderly even though they are particularly susceptible to the characteristics of their interior spaces. It is a well‐known fact that to be old is to acquire a tolerance of disabilities based on the gradual degeneration. A common problem is a dysfunction in visual sensitivity and accordingly, the alteration of their environmental color perception. That is why these impairments need to be understood in order to minimize the elderly spatial difficulties. To know at what point there is a loss in the ability to perceive color is necessary to understand how should we take these facts into consideration. A state‐of‐the‐art literature review of current studies from the last 20 years is carried out. The aim is to analyze existing practices on Evidence‐Based Research through a multidisciplinary approach in order to create knowledge about chromatic built environments for the elderly. Data are identified and considered together with empirical experience about color, perception, built environment and elderly. Thus, the way in which elderly perceive the space is explored. The adjustments in the formulation of these impairments throughout any design strategy to adapt the environment to their physiological changes are determined. This article aims to determine a design interpretation of the various findings, demonstrating that color, as a parameter of the visual performance, influences visual comfort and helps performance in architecture for old people.     

A viscoelastic–viscoplastic modeling approach for amorphous polymers in vacuum forming simulation

In this study, the simulation of a vacuum forming process employing a micromechanical inspired viscoelastic–viscoplastic model is investigated. In the vacuum forming process, a plastic sheet is heated above the glass transition temperature and subsequently forced into a mold by applying a vacuum. The model consists of a generalized Maxwell model combined with an dissipative element in series. Each Maxwell element incorporates a hyperelastic element in series with a viscous element based on a hyperbolical law. While the generalized Maxwell model considers the relaxation due to molecular alignment, the additional viscous element is a modification based on the approach of Bergström and thus considers molecular chain reptation. The model is designed with the aim to converge to the generalized linear Maxwell model in the limit of small deformation. Furthermore, the viscous modeling is temperature activated and follows the Williams–Landel–Ferry approach in the limit of linear viscoelasticity. To simulate rheological standard experiments, a physical-network-based implementation into Simscape is presented. To validate the performance of the model in thermoforming, it is implemented into Fortran programming language for finite element simulation with Abaqus/Explicit. It can be shown that the simulation is able to predict the thickness in high correlation with experimental results.     

Formation of phenazine from azobenzene over H-ZSM5: Reaction control by a molecular constrained environment

Azobenzene undergoes a unique reaction in the channels of H-ZSM5 zeolite at 593–673 K to give phenazine which is mainly retained within the zeolite. The yield of phenazine is increased by the addition to the reaction carrier gas of oxygen (1% vol.) which probably functions as a hydrogen acceptor. No reaction occurs when low acidity silicalite is used. On H-USY zeolite the yield of phenazine is low and the main product is a black, insoluble material which is probably polymeric. Benzo(c)cinnoline which is a known dehydrocyclization product from azobenzene under strongly acidic reaction conditions is never more than a trace product using H-ZSM5 or H-USY. A reaction scheme is proposed involving homolysis of the N ~ N bond in protonated trans-azobenzene, forming two radicals which, in a H-ZSM5 channel, are constrained in their mutual orientation so as to lead to the formation of phenazine.     

Equilibrium distribution of water in the two-phase system supercritical carbon dioxide–textile

When natural fibres are dyed in supercritical carbon dioxide, the addition of a small amount of water increases coloration. For a process design it is important to know how much water has to be added to obtain a desired humidity of both textile and carbon dioxide. In this work a thermodynamic model is proposed to calculate the distribution of water over the textile phase and the supercritical phase as a function of pressure and temperature. The phase equilibrium is described with Raoult's law for non-ideal fluids. The absorbed water in the textile is a condensed phase and is modelled here as a non-ideal liquid, using the NRTL-equation. The non-ideality of the supercritical phase is described by a solubility enhancement factor, a new equation derived from statistical thermodynamics. Although the model is applied to cotton, viscose, silk and wool, it can be used for all water absorbing textiles.     

Mechanism of micro-particle motion across falling liquid cylinder for PM2.5 separation (Ⅰ)Trajectory of particle motion towards surface and separation radius

提出了横掠液柱流的速度场和温度场推动PM_2.5微粒附面运动机理,建立了微粒附面运动微分方程和数值积分反演方法,计算粒子运动轨迹并预测可吸收的微粒运动最大分离半径。定义最大分离半径与液柱表面之间附面层的厚度为分离厚度,以气溶胶流体通过该区域的体积流量与横掠单液柱的总体积流量之比代表单液柱吸收效率;热泳推动力是强化吸收效率的主要因素。基于单液柱吸收效率,按串联模型导出规则排列的液柱群整体分离效率计算公式,依据液柱交叉流几何结构、流体流动和气液两相传热传质参数即可确定整体分离效率。对交叉流Reynolds数为170的实例计算显示,直径4 mm的单液柱吸收效率为1.18%,由195排液柱群组成的长度为1170 mm的分离通道整体分离效率达到90%。     

Color separation for colored fiber blends based on the fuzzy C‐means cluster

Colored fibers can be blended in a certain proportion to achieve a specific color. It is a very hard task for the colorist to find a good recipe to meet the final product without the aid of computer. In this article, a color separation method for the colored fiber blends is discussed to substitute for some manual work. The fuzzy C‐means cluster is a way to group the color in the colored fiber blends image. The distance index, which is a key factor during the fuzzy C‐means cluster process, is calculated in the RGB color space and the HSV color space with some transformation. The final experiment result proved that the colors of each pixel in the blends' image can be replaced by corresponding cluster center associating colors in the HSV color space, and the main texture as well as the main color information about the fibers in the image is preserved. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012     

Contact time of an incident particle hitting a 2D bed of particles

Removal of particles from fouling layers due to an incident particle impact is affected by the fluid fluctuations in industrial applications if the contact time is larger than the fluctuations time scales. The contact time is an important parameter when analysing the influence of the fluid structure interaction on a fouling process. The contact time for a particle hitting a bed of particles is defined as the time it takes for the incident particle to bounce off the bed. The contact time for a particle hitting a bed of particles arranged in a rectangular and a hexagonal array is measured experimentally and calculated numerically based on the discrete element method. The incident particle and the bed particles are of the same size and material. It is found that the contact time is proportional to the number of bed layers in case of a rectangular bed array and independent of the number of bed layers in case of a hexagonal bed of particles. The contact time is inversely proportional to the impact speed. The rebound speed of the incident particle is independent of the number of bed layers in case of a hexagonal arrangement of particles and is exponentially dependent on the number of bed layers in case of a rectangular arrangement. A hexagonal bed of particles acts as a massive particle due to its large co-ordination number compared to a rectangular bed of particles. The force propagation speed in granular matter could be calculated by plotting the path of the force as a function of the contact time and finding the gradient of this graph.     

Investigation in thermal endurance of polyesterimide used in electrical machines

The purpose of this investigation is to evaluate thermal lifetime of polyesterimide using Weibull statistics. Thermal aging was performed on twisted pair specimens of copper wire insulated by a polyesterimide layer. The study shows that breakdown voltage varies versus aging time. Its increase is allotted to a crosslinking inducing a diminution of mean‐free path of charge carriers leading thereby to a mobility decrease, whereas its decrease is attributed to the viscosity diminution expressing a weakening of molecular bonds and a mobility increase of charge carriers. Shape parameter changes in function of aging time. Its increase is ascribed to an arrangement of the molecular structure, whereas its decrease is due to an augmentation in the size of defects. The thermal endurance graph is a straight line indicating that the degradation is governed by a first‐order chemical reaction. Activation energy and temperature index were determined. The degradation is governed by the dissolution of copper into the polymer and accelerates its degradation occurring at the polyesterimide–copper interface. Oxygen can diffuse into the insulation and attack copper resulting in the formation of copper oxide. The degradation is caused by the scission of imide and ester bonds. The process is followed by a change in color and a presence of cracks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Milk skin formation during drying

Mass transfer during the drying of skim milk and whole milk films is examined using a combination of experiments and mathematical modeling. Microwave power is used rather than the traditional convective heating characteristic of spray drying to provide greater heating uniformity. In all experiments a period of constant rate drying is observed, followed by a period of diffusion control that is characterised by a rapid increase in sample temperature. The onset of diffusion control is shown to be directly related to the amount of both fat and protein in whole milk samples and to the amount of protein in skim milk samples. These changes occur as a result of the lower diffusivity of protein and fat relative to other milk solids. Over time this difference in diffusivities causes these higher molecular weight solids to segregate from the remaining solids, forming a thickening milk skin. The skim milk data has been successfully fitted to a moisture transport model that incorporates such a milk skin region. The diffusion coefficient within the skin is proportionately lower than in the bulk. The simulated rate of skin thickening is observed to be a simple function of the sample protein content and the sample temperature.     

Single-phase flow model development for macroscopic liquid flow evaluation in gas–liquid reactors, by computational fluid dynamics

This paper proposes a single-phase flow model to simulate the flow induced in a liquid by the injection of gas dispersed in the form of a bubble curtain. It aims at predicting macroscopic liquid flow and mixing time. This single-phase flow model is developed as an alternative to two-phase flow models. The model is based on the assumption that the liquid flow is induced by a density imbalance between the bulk zone and the bubble curtain zone. The density in the bulk is set to the water density while the density in the bubble curtain corresponds to the air–water mixture density and is assessed by numerical simulations, thanks to an iterative procedure. Only the knowledge of the injected air flow rate and the bubble liquid relative velocity is required. The single-phase flow model is applied to assess the liquid flow and the mixing in open quarries having a complex geometry. The liquid velocities and the flow structure in the open quarries simulated with the single-phase flow model are in good agreement with those predicted by numerical simulations based on a two-phase flow model.     

High solids content emulsion polymerisation without intermediate seeds. Part I. Concentrated monomodal latices

In order to produce high solid content latexes in an unseeded process it is necessary to first begin by generating a concentrated latex with a monomodal particle size distribution and high solid contents. A process for the emulsion polymerisation of methyl methacrylate with butyl acrylate at solid contents of over 60% per unit volume is presented. The process relies on the use of an electrically neutral initiation system, combined with a stabilisation system rich in non-ionic surfactant. It was demonstrated that during the critical semi-batch growth stage, it is necessary to add the surfactant at a variable flow rate in order to avoid accumulating it in the water phase, and thereby ensuring that particles created by homogeneous nucleation are not stabilised. It is also shown that correctly adjusting the flow rate leads to a robust, reproducible process. Finally, a ‘stability band’ is clearly identified, and it is clear that the system is ‘self-regulating’ in the sense that an equilibrium between auto-flocculation and stabilisation of new particles leads to a latex with a surface coverage of 80-95% at high solid contents.     

Characterization of photodegradation of a polyurethane coating by positron annihilation spectroscopy: correlation with cross-link density

Photodegradation of a polyurethane coating by Xe arc-lamp irradiation as a function of time is studied by positron annihilation spectroscopy. Doppler broadening energy spectra (DBES) of annihilation irradiation is measured as a function of incident positron energy (0–30 keV). A significant decrease in the S-defect parameter from DBES is observed as a function of irradiation time. This is interpreted as a loss of free-volume and holes during the photodegradation process. The cross-link density in the same system is measured by a solvent (methylene chloride) swelling method and is found to increase as a function of irradiation time. A direct correlation between the increase in cross-link density and the decrease in the S-defect parameter from the DBES data is observed. These results are used to discuss the photodegradation process in terms of chemical and physical changes due to UV-irradiation in protective polymeric systems.     

Modelling of a clinker rotary kiln using operating functions concept

Modelling and parameter identification of complex dynamic systems/processes is one of the main challenging problems in control engineering. An example of such a process is clinker rotary kiln (CRK) in cement industry. In the prevailing models independently of which structure is used to describe the kiln's dynamics and the identification algorithm, parameters are assumed to be centralised and constant while the CRK is well known as a distributed parameter system with a strongly varying dynamic through time. In this work, the kiln's dynamic is described in the form of a state‐space representation with three state variables using a system of partial differential equations (PDE). The structure is chosen so that it can easily be embedded in classical state‐space control algorithms. The parameters of the PDE system are called operating functions since their numerical values vary with respect to different operating conditions of the kiln, to their position in the kiln, and through time. A phenomenological approach is also proposed in this paper to identify the operating functions for a given steady‐state operation of the kiln. The model is then used to perform a semi‐dynamic simulation of the process through manipulating main process variables.     

Flash cosintering of a lanthanum strontium cobalt ferrite nanofibre/Gd-doped ceria bilayer structure

For solid oxide fuel cells, an important structural requirement is that the electrolyte layer needs to be dense and the electrode layer porous, which is difficult to obtain by conventional cosintering. In this work, flash cosintering of a double layer structure consisting of a Gd-doped ceria substrate with a lanthanum strontium cobalt ferrite nanofibre coating is investigated. Experimental and finite element modelling results reveal that when the LSCF layer is connected to the electrode, the heat is concentrated in the LSCF layer, which leads to a huge temperature gradient and introduces severe cracking. When the LSCF layer is electrically isolated from the electrode, the heat is concentrated in the GDC layer, and the temperature gradient is dramatically reduced. In this situation, the density of GDC can reach 92.86% while a high porosity of 52.26% is maintained in the LSCF layer, which is higher than that of the conventional cosintered sample.     

A Reliable Method to Measure the Adhesive Force with a Tiny Amount of Adhesive Material

A new method is proposed and developed to measure adhesive forces by use of the force-distance curve of a micro cantilever with an extremely small amount of testing material such as adhesive proteins. The contact area should be well-controlled at a reasonable value. Even though the area is desired to be as small as possible, a contact region of several micrometers by several micrometers is adopted in order to avoid obtaining meaningless measured values and uncertainty in the contact areas. An AFM cantilever is used after having been modified with a micro glass bead to enlarge the contact area for adhesion. A glass plate with micro-scale circular patterns is fabricated from a glass wafer by micro-machining processes in order to control precisely the contact area in adhesion tests. In the proposed method the adhesive materials are directly applied to the bead attached at the AFM cantilever before it is applied on the top area of the truncated cone on the fabricated glass plate. The developed method is applied to measure the adhesive forces of Cell-Tak® (which is a commercial extracted mussel adhesive) and recombinant Mgfp-5 (which is a recombinant mussel adhesive protein) and the statistical credibility of the measured adhesive force data is enormously improved as a result.     

A Reliable Method to Measure the Adhesive Force with a Tiny Amount of Adhesive Material

A new method is proposed and developed to measure adhesive forces by use of the force-distance curve of a micro cantilever with an extremely small amount of testing material such as adhesive proteins. The contact area should be well-controlled at a reasonable value. Even though the area is desired to be as small as possible, a contact region of several micrometers by several micrometers is adopted in order to avoid obtaining meaningless measured values and uncertainty in the contact areas. An AFM cantilever is used after having been modified with a micro glass bead to enlarge the contact area for adhesion. A glass plate with micro-scale circular patterns is fabricated from a glass wafer by micro-machining processes in order to control precisely the contact area in adhesion tests. In the proposed method the adhesive materials are directly applied to the bead attached at the AFM cantilever before it is applied on the top area of the truncated cone on the fabricated glass plate. The developed method is applied to measure the adhesive forces of Cell-Tak® (which is a commercial extracted mussel adhesive) and recombinant Mgfp-5 (which is a recombinant mussel adhesive protein) and the statistical credibility of the measured adhesive force data is enormously improved as a result.