17 results
Search Results
2. Modeling-Guided Design of Paper Microfluidic Networks: A Case Study of Sequential Fluid Delivery
- Author
-
Dharitri Rath and Bhushan J. Toley
- Subjects
Paper ,Optimal design ,Reverse engineering ,Computer science ,Microfluidics ,Bioengineering ,02 engineering and technology ,computer.software_genre ,01 natural sciences ,Lab-On-A-Chip Devices ,Instrumentation ,Immunoassay ,Fluid Flow and Transfer Processes ,Mathematical model ,Process Chemistry and Technology ,010401 analytical chemistry ,Control engineering ,Microfluidic Analytical Techniques ,021001 nanoscience & nanotechnology ,Trial and error ,0104 chemical sciences ,Flow (mathematics) ,Richards equation ,0210 nano-technology ,Convection–diffusion equation ,computer - Abstract
Paper-based microfluidic devices are popular for their ability to automate multistep assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behavior. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without experimental trial and error. This was accomplished by three new developments in modeling flow through paper networks: (i) coupling of the Richards equation of flow through porous media to the species transport equation, (ii) modeling flow through assemblies of multiple paper materials (test membrane and wicking pad), and (iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks. ©
- Published
- 2020
3. Quantitative study on the aging of kraft paper in vegetable oils.
- Author
-
Carcedo, Juan, Fernandez, Inmaculada, Ortiz, Alfredo, Delgado, Fernando, Renedo, Carlos J., and Arroyo, Alberto
- Subjects
KRAFT paper ,VEGETABLE oils ,COOLANTS ,VISCOSITY ,MINERAL oils - Abstract
Interest in using vegetable oils as dielectric coolants in power transformers dates back to the early studies on linseed- and castor- based fluids as possible replacements of mineral oil. However, interest in vegetable oils was lost due to their high viscosity and their tendency to oxidize. But, in the early 1990s and due to environmental concerns, the interest in dielectric fluids based on vegetable esters re-emerged. As a result, two vegetable ester? based oils were developed, namely, BIOTEMP, developed by ABB, and FR3?, developed by Cooper Power Systems. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
4. Analysis of insulating state on transformer model using PDC method.
- Author
-
Jurcik, Jozef
- Abstract
Paper is about mathematical interpretation of transformer insulation system. Base of this system is composed by two elements oil and paper. We need to simulate this system for more precisely results from measurement. Section three describes how to calculate relaxation currents and how that currents are generated. So we are able to compare measured and computed values and deduce actual condition of this insulation system. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
5. Inner insulation structure optimization of UHV RIP oil-SF6 bushing using electro-thermal simulation and advanced equal margin design method.
- Author
-
Zhang, Shiling, Peng, Zongren, and Liu, Peng
- Subjects
- *
ELECTRIC insulators & insulation , *HIGH voltages , *BUSHINGS , *STRUCTURAL optimization , *FINITE element method , *PAPER - Abstract
The iso-margin method based on the classical analytical equations is widely used in the development of extra high voltage (EHV) bushing. Therefore, its effectiveness and feasibility have been fully validated. However, with the theoretical formula, it is difficult to evaluate the influence of stray capacitance and temperature on the internal electric stress of the ultra high voltage (UHV) bushing. It?s necessary to further improve the traditional iso-margin method. Firstly, the basic principle of iso-margin method has been briefly described. After that, the E-field distribution of condenser bushing was investigated on the Finite Element Method (FEM) computing platform. Then, the mathematical model of the advanced equal margin design method was established. Furthermore, this paper presents the program flow of optimization which combines the simulation of electro-thermal coupling process and the particle swarm optimization (PSO) algorithm. The proposed methodology was applied to the design of the prototype of the UHV resin impregnated paper (RIP) oil-SF6 bushing, which realizes the uniform axial E-field distribution of the bushing condenser. Meanwhile, the partial discharge margin between adjacent foils can be equal. Moreover, the hot-spot temperature is lower than the operation limiting temperature of the RIP material. The bushing condenser was fabricated according to the optimal structure design. The prototype of bushing has passed through all the type tests. In this paper, the FEM electro-thermal coupling simulation and the advanced equal margin design method were applied to the inner insulation structure optimization of the UHV RIP oil-SF6 bushing. Meanwhile, the proposed methodology provides some theoretical guidelines for the future research and development of other types of bushing on the UHV level. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
6. Modelling migration from paper into a food simulant
- Author
-
Poças, Maria de Fátima, Oliveira, Jorge C., Pereira, Joel R., Brandsch, Rainer, and Hogg, Timothy
- Subjects
- *
DIFFUSION , *PAPER , *MATHEMATICAL models , *PHTHALATE esters , *FOOD packaging , *FOOD chemistry , *WASTE recycling , *PULPING - Abstract
Abstract: The migration of components from paper into Tenax® was studied to determine the influence of molecular size and chemical character of the migrant and the influence of paper characteristics in the migration process. The Weibull model was applied because Fick’s 2nd law of diffusion gave poor fits in some cases. The migration pattern depended on the migrants molecular size and was independent of temperature in the studied range. The migration rate decreased with the migrant molecular size. The influence of the migrants character (polarity and vapour pressure) on the migration behaviour was also studied: nonpolar migrants with high vapour pressure presented low relative migration values and polar migrants presented high values of relative migration. Results indicated that the apparent partition coefficient between paper and the simulant Tenax® increased with the migrant vapour pressure and with both the paper grammage and the recycled pulp content. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
7. An anisotropic fibre-network model for mechano-sorptive creep in paper
- Author
-
Strömbro, Jessica and Gudmundson, Peter
- Subjects
- *
WEATHER , *METEOROLOGY , *ATMOSPHERIC water vapor , *MOISTURE - Abstract
Abstract: In this paper a simplified network model for mechano-sorptive creep is presented, which is a further development of an earlier paper [Strömbro, J., Gudmundson, P., 2008. Mechano-sorptive creep under compressive loading – a micromechanical model. International Journal of Solids and Structures 45 (9), 2420–2450.]. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive effects in compression than in tension. Moisture dependent material parameters and anisotropy in the fibre distribution have been introduced. Theoretical predictions based on the model are compared to experimental results for an anisotropic paper both under tensile and compressive loading at varying moisture content and it is found that the important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
8. Mechano-sorptive creep under compressive loading – A micromechanical model
- Author
-
Strömbro, Jessica and Gudmundson, Peter
- Subjects
- *
MOISTURE , *HUMIDITY , *MICROMECHANICS , *SOLID state physics - Abstract
Abstract: The creep of paper is accelerated by moisture cycling, an effect known as mechano-sorptive creep. It has also been observed that the mechano-sorptive effects are larger in compression than in tension. In this paper a simplified network model for mechano-sorptive creep is presented. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre–fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys constitutive laws that are non-linear in stress. Geometrical fibre effects are included in the model in order to capture experimental observations of the differences between paper loaded in tension and compression. Theoretical predictions based on the developed model are compared to experimental results for paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model, i.e. the creep is accelerated by the moisture cycling and the mechano-sorptive effects are larger in compression than in tension. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
9. Heat and mass transfer in multicylinder drying: Part I. Analysis of machine data
- Author
-
Nilsson, Lars
- Subjects
- *
MASS transfer , *HEAT transfer , *MATHEMATICAL models , *PAPER , *DRYING - Abstract
A mathematical model describing the heat and mass transfer in the dryer section of a paper machine has been applied to the production data from four paper machines. Model predictions for the machine speed are compared to actual machine speeds for a total of 163 data sets. The mathematical model assumes that the temperature and moisture content remain homogeneous in the thickness direction of the sheet. For three paper machines producing paper with basis weights ranging from 0.056 to 0.159 kg d.s./m2 the model predictions are adequate. For the paper machine producing the heaviest grades with basis weights ranging from 0.189 to 0.390 kg d.s./m2 the model predictions are flawed by a systematic error. For low machine velocities/high basis weights the machine velocity is over-predicted and for high machine velocities/low basis weights the machine velocity is under-predicted. This systematic error is caused by the assumption of homogeneous moisture content and temperature within the sheet being severely in error for thick sheets. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
10. Heat and mass transfer in multicylinder drying: Part II. Analysis of internal and external transport resistances
- Author
-
Nilsson, Lars
- Subjects
- *
MASS transfer , *HEAT transfer , *MATHEMATICAL models , *PAPER , *DRYING - Abstract
The present study investigates two models—two limiting cases—for the internal heat and mass transfer in a multicylinder dryer: the first model assumes that complete redistribution of heat and moisture in the thickness direction occurs instantaneously. The second model assumes that moisture transfer occurs only by vapor diffusion and that heat transfer takes place by conduction and condensation. The two models are written in dimensionless form, and applied for the same set of standard paper machine data. For basis weights below approximately 0.05 kg d.s./m2 the results are so close that the first, simple model is sufficient. A higher limiting basis weight—approximately 0.16 kg d.s./m2—was previously indicated by comparison of model predictions, assuming the simple model, to extensive sets of machine data from four different paper machines. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
11. Multilayered Microfluidic Paper-Based Devices: Characterization, Modeling, and Perspectives
- Author
-
Michael P. Nguyen, Robert B. Channon, Charles S. Henry, and David S. Dandy
- Subjects
Paper ,Mathematical model ,Capillary action ,Chemistry ,010401 analytical chemistry ,Microfluidics ,Mechanical engineering ,Microfluidic Analytical Techniques ,010402 general chemistry ,Fluid transport ,01 natural sciences ,Article ,0104 chemical sciences ,Analytical Chemistry ,Volumetric flow rate ,Models, Chemical ,Lab-On-A-Chip Devices ,Fluid dynamics ,Porous medium ,Communication channel - Abstract
Microfluidic paper-based analytical devices (μPADs) are simple but powerful analytical tools that are gaining significant recent attention due to their many advantages over more traditional monitoring tools. These include being inexpensive, portable, pump-free, and having the ability to store reagents. One major limitation of these devices is slow flow rates, which are controlled by capillary action in the hydrophilic pores of cellulosic paper. Recent investigations have advanced the flow rates in μPADs through the generation of a gap or channel between two closely spaced paper sheets. This multilayered format has opened up μPADs to new applications and detection schemes, where large gap sizes (>300 μm) provide at least 169× faster flow rates than single-layer μPADs, but do not conform to established mathematical models for fluid transport in porous materials, such as the classic Lucas-Washburn equation. In the present study, experimental investigations and analytical modeling are applied to elucidate the driving forces behind the rapid flow rates in these devices. We investigate a range of hypotheses for the systems fluid dynamics and establish a theoretical model to predict the flow rate in multilayered μPADs that takes into account viscous dissipation within the paper. Device orientation, sample addition method, and the gap height are found to be critical concerns when modeling the imbibition in multilayered devices.
- Published
- 2019
12. An anisotropic fibre-network model for mechano-sorptive creep in paper
- Author
-
Peter Gudmundson and Jessica Strömbro
- Subjects
Paper ,Fibre network ,Materials science ,Fiber network ,Modelling ,Mathematical model ,Materials Science(all) ,Modelling and Simulation ,Accelerated creep ,Fibre bonding ,General Materials Science ,Moisture changes ,Humidity change ,Composite material ,Anisotropy ,Network model ,Tension (physics) ,Mechanical Engineering ,Applied Mathematics ,Compression ,Fibres ,Creep ,Compression (physics) ,Condensed Matter Physics ,Mechano-sorptive creep ,Tension ,Mechanics of Materials ,Modeling and Simulation ,Sorption - Abstract
In this paper a simplified network model for mechano-sorptive creep is presented, which is a further development of an earlier paper [Strömbro, J., Gudmundson, P., 2008. Mechano-sorptive creep under compressive loading – a micromechanical model. International Journal of Solids and Structures 45 (9), 2420–2450.]. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive effects in compression than in tension. Moisture dependent material parameters and anisotropy in the fibre distribution have been introduced. Theoretical predictions based on the model are compared to experimental results for an anisotropic paper both under tensile and compressive loading at varying moisture content and it is found that the important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined.
- Published
- 2008
- Full Text
- View/download PDF
13. Mechano-sorptive creep under compressive loading – A micromechanical model
- Author
-
Peter Gudmundson and Jessica Strömbro
- Subjects
Paper ,Fibre network ,Materials science ,Fiber network ,Modelling ,Physics::Geophysics ,Mathematical model ,Materials Science(all) ,Modelling and Simulation ,Accelerated creep ,Fibre bonding ,General Materials Science ,Moisture changes ,Humidity change ,Composite material ,Moisture ,Tension (physics) ,Applied Mathematics ,Mechanical Engineering ,Compression ,Fibres ,Creep ,Condensed Matter Physics ,Compression (physics) ,Micromechanical model ,Network model ,Compressive load ,Mechano-sorptive creep ,Tension ,Mechanics of Materials ,Modeling and Simulation ,Sorption - Abstract
The creep of paper is accelerated by moisture cycling, an effect known as mechano-sorptive creep. It has also been observed that the mechano-sorptive effects are larger in compression than in tension. In this paper a simplified network model for mechano-sorptive creep is presented. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre–fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys constitutive laws that are non-linear in stress. Geometrical fibre effects are included in the model in order to capture experimental observations of the differences between paper loaded in tension and compression. Theoretical predictions based on the developed model are compared to experimental results for paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model, i.e. the creep is accelerated by the moisture cycling and the mechano-sorptive effects are larger in compression than in tension.
- Published
- 2008
14. Water network cost optimization in a paper mill based on a new library of mathematical models
- Author
-
F. Claeys, L. Sancho, M. de Gracia, I. Lizarralde, P. Grau, and Ruth Ordóñez
- Subjects
Paper ,Engineering ,Environmental Engineering ,Total cost ,Water supply ,Industrial Waste ,02 engineering and technology ,computer.software_genre ,Waste Disposal, Fluid ,Water Purification ,0202 electrical engineering, electronic engineering, information engineering ,Process engineering ,Representation (mathematics) ,Simulation ,Water Science and Technology ,Electronic circuit ,Mathematical model ,business.industry ,020208 electrical & electronic engineering ,Models, Theoretical ,021001 nanoscience & nanotechnology ,6. Clean water ,Software framework ,Wastewater ,Management system ,0210 nano-technology ,business ,computer ,Water Pollutants, Chemical - Abstract
The increasing costs associated with water supply and the disposal of wastewater has stimulated industries to seek more efficient water management systems. Mathematical modelling and simulation can be a very valuable tool for the study of the multiple alternatives available whilst assessing optimum solutions for water management in industry. This study introduces a new steady state model library able to reproduce industrial water circuits. It has been implemented in a novel software framework for the representation, simulation and optimization of industrial water networks. A water circuit representing a paper mill has been modelled and simulated showing the capability to reproduce real case studies. Alternative scenarios for the water network have also been tested to assess the capability of the models to optimize water circuits minimizing total cost.
- Published
- 2012
15. Modelling migration from paper into a food simulant
- Author
-
Maria de Fátima Tavares Poças, Tim Hogg, Jorge C. Oliveira, Rainer Brandsch, Joel Pereira, and Veritati - Repositório Institucional da Universidade Católica Portuguesa
- Subjects
Paper ,Grammage ,Chromatography ,Chemistry ,Vapor pressure ,Diffusion ,Thermodynamics ,social sciences ,Migration modelling ,female genital diseases and pregnancy complications ,Mathematical model ,Molecular size ,Phthalates ,Packaging ,Tenax ,Phthalate ,behavior and behavior mechanisms ,population characteristics ,Board ,Recycling ,geographic locations ,Migration ,Food Science ,Biotechnology - Abstract
The migration of components from paper into Tenax® was studied to determine the influence of molecular size and chemical character of the migrant and the influence of paper characteristics in the migration process. The Weibull model was applied because Fick's 2nd law of diffusion gave poor fits in some cases. The migration pattern depended on the migrants molecular size and was independent of temperature in the studied range. The migration rate decreased with the migrant molecular size. The influence of the migrants character (polarity and vapour pressure) on the migration behaviour was also studied: nonpolar migrants with high vapour pressure presented low relative migration values and polar migrants presented high values of relative migration. Results indicated that the apparent partition coefficient between paper and the simulant Tenax® increased with the migrant vapour pressure and with both the paper grammage and the recycled pulp content.
- Published
- 2011
16. Micro-mechanical mechanisms for deformation in polymer-material structures
- Author
-
Strömbro, Jessica
- Subjects
Paper ,Moisture change ,Length-scale effects ,Particle composite ,Fibre model ,Micro-indentation ,Strain gradient ,Network model ,Mathematical model ,Mechano-sorptive creep ,Annan materialteknik ,Interfacial debonding ,Accelerated creep ,Other Materials Engineering ,Humidity change ,Polymer ,Matrix cracking - Abstract
In this thesis, the focus has been on micro-mechanical mechanisms in polymer-based materials and structures. The first part of the thesis treats length-scale effects on polymer materials. Experiments have showed that the smaller the specimen, the stronger is the material. The length-scale effect was examined experimentally in two different polymers materials, polystyrene and epoxy. First micro-indentations to various depths were made on polystyrene. The experiments showed that length-scale effects in inelastic deformations exist in polystyrene. It was also possible to show a connection between the experimental findings and the molecular length. The second experimental study was performed on glass-sphere filled epoxy, where the damage development for tensile loading was investigated. It could be showed that the debond stresses increased with decreasing sphere diameter. The debonding grew along the interface and eventually these cracks kinked out into the matrix. It was found that the length to diameter ratio of the matrix cracks increased with increasing diameter. The experimental findings may be explained by a length-scale effect in the yield process which depends on the strain gradients. The second part of the thesis treats mechano-sorptive creep in paper, i.e. the acceleration of creep by moisture content changes. Paper can be seen as a polymer based composite that consists of a network of wood fibres, which in its turn are natural polymer composites. A simplified network model for mechano-sorptive creep has been developed. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre-fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear in stress. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive creep effects in compression than in tension. Furthermore, moisture dependent material parameters and anisotropy are taken into account. Theoretical predictions based on the developed model are compared to experimental results for anisotropic paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. QC 20100910
- Published
- 2008
17. Modelling and analysing oriented fibrous structures
- Author
-
Jouni Sampo, Jouni Takalo, Jussi Timonen, Maaria Rantala, Matti Lassas, Samuli Siltanen, and Department of Mathematics and Statistics
- Subjects
wood fibres ,REPRESENTATION ,History ,Scaling law ,Ground truth ,Mathematical model ,fibrous structures ,IMAGE ,Computer science ,Orientation (computer vision) ,Curvelet transform ,Computer Science Applications ,Education ,Orientation analysis ,PAPER ,111 Mathematics ,Curvelet ,CONTINUOUS CURVELET TRANSFORM ,Representation (mathematics) ,Algorithm - Abstract
A mathematical model for fibrous structures using a direction dependent scaling law is presented. The orientation of fibrous nets (e.g. paper) is analysed with a method based on the curvelet transform. The curvelet-based orientation analysis has been tested successfully on real data from paper samples: the major directions of fibrefibre orientation can apparently be recovered. Similar results are achieved in tests on data simulated by the new model, allowing a comparison with ground truth. peerReviewed
- Published
- 2014
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.