http://hdl.handle.net/10993/83 Search this channel search http://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/41878 Title: Covalent functionalization of graphene oxide with D-mannose: evaluating the hemolytic effect and protein corona formation <br/> <br/>Author, co-author: Sousa, Marcelo De; Martins, Carlos H. Z.; Franqui, Lidiane S.; Fonseca, Leandro C.; Delite, Fabrício S.; Martin Lanzoni, Evandro; Martinez, Diego Stéfani T.; Alves, Oswaldo L. <br/> <br/>Abstract: In this work, graphene oxide (GO) was covalently functionalized with D-mannose (man-GO) using mannosylated ethylenediamine. XPS (C1s and N1s) confirmed the functionalization of GO through the binding energies at 288.2 eV and 399.8 eV, respectively, which are attributed to the amide bond. ATR-FTIR spectroscopy showed an increase in the amine bond intensity, at 1625 cm−1 (stretching CO), after the functionalization step. Furthermore, the man-GO toxicity to human red blood cells (hemolysis) and its nanobiointeractions with human plasma proteins (hard corona formation) were evaluated. The mannosylation of GO drastically reduced its toxicity to red blood cells. SDS-PAGE analysis showed that the mannosylation process of GO also drastically reduced the amount of the proteins in the hard corona. Additionally, proteomics analysis by LC–MS/MS revealed 109 proteins in the composition of the man-GO hard corona. Finally, this work contributes to future biomedical applications of graphene-based materials functionalized with active biomolecules. http://hdl.handle.net/10993/40182 Title: Isotropic–isotropic phase separation and spinodal decomposition in liquid crystal–solvent mixtures <br/> <br/>Author, co-author: Reyes, Catherine; Baller, Jörg; Araki, Takeaki; Lagerwall, Jan <br/> <br/>Abstract: Phase separation in mixtures forming liquid crystal (LC) phases is an important yet under- appreciated phenomenon that can drastically influence the behaviour of a multi-component LC. Here we demonstrate, using polarising microscopy with active cooling as well as differential scanning calorimetry, that the phase diagram for mixtures of the LC-forming compound 4’-n- pentylbiphenyl-4-carbonitrile (5CB) with ethanol is surprisingly complex. Binary mixtures reveal a broad miscibility gap that leads to phase separation between two distinct isotropic phases via spinodal decomposition or nucleation and growth. On further cooling the nematic phase enters on the 5CB-rich side, adding to the complexity. Significantly, water contamination dramatically raises the temperature range of the miscibility gap, bringing up the critical temperature for spinodal de- composition from ∼ 2◦C for the anhydrous case to > 50◦C if just 3 vol.% water is added to the ethanol. We support the experiments with a theoretical treatment that qualitatively reproduces the phase diagrams as well as the transition dynamics, with and without water. Our study highlights the impact of phase separation in LC-forming mixtures, spanning from equilibrium coexistence of multiple liquid phases to non-equilibrium effects due to persistent spatial concentration gradients. http://hdl.handle.net/10993/40004 Title: A DEM approach for modeling biomass fast pyrolysis in a double auger reactor <br/> <br/>Author, co-author: Qi, Fenglei <br/> <br/>Abstract: Thermochemical conversion of biomass via fast pyrolysis process is a promising way to produce renewable fuels and chemicals. In this paper, an extended discrete element method (DEM) is developed to predict the biomass fast pyrolysis process in a double auger reactor, which is described as a reacting granular flow. The thermodynamic state of each particle is properly predicted with an addition of a heat transfer model and a reaction model on top of the traditional DEM method. The results suggest that the predictions of the thermochemical decomposition kinetics of biomass components are consistent with the experimental observations. The results also indicate that the fast pyrolysis in the reactor is controlled by the heat transfer process. Any operating condition variation in favor of enhancing heat transfer is beneficial to the fast pyrolysis process and vice versa. http://hdl.handle.net/10993/39533 Title: Confined in a Fiber: Realizing Flexible Gas Sensors by Electrospinning Liquid Crystals <br/> <br/>Author, co-author: Reyes, Catherine <br/> <br/>Abstract: Liquid crystalline phases (LCs) readily exhibit optical responsivity to small fluctuations in their immediate environment. By encapsulating LC phase forming compounds within polymer fibers through the electrospinning process (a fiber spinning method known for being a fast way of forming chemically diverse non-woven mats), it is possible to create functionalized LC-polymer fiber mats that are responsive as well. As these fiber mats can be handled macroscopically, a usercan observe the responses of the mats macroscopically without the need for bulky electronics. This thesis presents several non-woven fiber mats that were coaxially electrospun to contain LC within their individual polymer fibers cores for use as novel volatile organic compound (VOC) sensors. The mats are flexible, lightweight, and shown to both macroscopically and microscopically respond to toluene gas. Such gas responsive mats may be incorporated into garments for visually alerting the wearer when they are exposed to harmful levels of VOCs for example. Additionally, the interaction and re-prioritization of several electrospinning variables (from the chemistry based to the processing based) for forming the LC-mats are also discussed. The balance of these variables determines whether a wide range of phenomena occur during fiber formation. For instance, unexpected phase separation between the polymer sheath solution and the LC core can mean the difference between forming fully dried fibrous mats and wet/meshed films. A chapter is devoted to discussing the impact that solvent miscibility with an LC can have on fiber production, including also the effect that water can have when condensed into the electrospinning coaxial jet. The fiber shapes that the polymer fiber sheaths adopt (beaded versus non-beaded), as well as the continuity of the LC core, will influence the visual app earance of the mats. These optical properties, in turn, influence the mats’ responsivity to gases and whether the responses can be macroscopically observed with or without additional polarizers. During two types of gas sensing experiments --mats exposed to gas when contained in a cell, and mats exposed to gas diffused in ambient air without containment, we see that not all fibers within a mat respond at the same time. Moreover, different segments of the fibers within the same non-woven mat also show slightly different rates of response due to variations in fiber thickness, LC content, and whether the fiber cores had variations in LC filling (i.e. LC director twists, and gaps). http://hdl.handle.net/10993/39528 Title: Comparison of numerical schemes for 3D Lattice Boltzmann simulations of moving rigid particles in thermal fluid flows <br/> <br/>Author, co-author: Rosemann, T; Kruggel-Emden, H; Wu, Mingqiu; Peters, Bernhard <br/> <br/>Abstract: The Lattice Boltzmann method is an efficient numerical method for direct numerical simulations of particulate flows. For a variety of applications not only the flow but also the heat transfer between particle and fluid plays an important role. While for non-thermal flows numerous techniques to handle the moving boundaries of particles have been developed, appropriate techniques for the thermal Lattice Boltzmann method are still lacking. The following three issues are of special importance. First, the thermal boundary conditions (Dirichlet or Neumann) have to be fulfilled on the particle surface. Second, reasonable values have to be found for temperature distributions in grid nodes that are uncovered by moving particles. Third, the heat transfer between particulate and fluid phase has to be evaluated in many application, since it is an essential quantity of interest. In this work, we present new numerical schemes for all of these three key aspects. They rely to a great degree on existing schemes for the non-thermal Lattice Botzmann method. In four benchmark cases we assess which of them are the most favourable and we also show to what extend schemes based on the same principles behave similarly or differently in the flow and heat transfer simulation. The results demonstrate that the proposed techniques deliver accurate results and allow us to recommend the most advantageous approach. http://hdl.handle.net/10993/39527 Title: A forcing fictitious domain/immersed boundary method for super-quadric shape of particulate flow simulation of cementitious material <br/> <br/>Author, co-author: Wu, Mingqiu; Peters, Bernhard; Dressler, Inka <br/> <br/>Abstract: Fictitious domain/immersed boundary method (FD/IBM) has recently been used for particulate flows and complex fluid-solid interaction problems. The advantage of FD/IBM over the body- fitted method is that it substantially simplifies grid generation for immersed geometries, and it is easier to handle moving boundary situations. FD/IBM even allows the use of a stationary and non- deformation background mesh, as well as it reduces the cost of computation by avoiding generation of a body-fitted mesh for each time step. In this work, we develop a new platform to directly simulate super-quadric (SQ) particles in fluid based on a forcing fictitious domain method. Specifically, a super-quadric particle function is used to represent particle with varying shapes and sizes as encountered for concrete and mortar. The immersion of particles in fluid is handled by imposing a rigidity solid body motion in the particle domain, as well as adding a forcing term to the Navier-stokes equation by integral of pressure gradient and particle related velocity over the whole particle domain. Particle shapes are given by changing the super-quadric parameters of SQ equation. Particle motions, which occur during pumping of cementitious material, can be calculated and tracked by solving Newton’s equations of motions using the extended discrete element method (XDEM)[4] while the data of fluid flow properties are obtained by solving the Navier-Stokes equations which govern the fluid phase. Hence, a particle interface resolving solver is developed by coupling XDEM and IBM. We validate our solver by performing flow around particles and free falling of a particle in the channel at different parameters in 2D and 3D. The final objective of this work is to develop a particle-resolved direct numerical simulation platform to predict highly packed fluids with different shapes of particles and over a wide range of particle sizes. http://hdl.handle.net/10993/39454 Title: Liquid transport rates during binary collisions of unequally-sized particles <br/> <br/>Author, co-author: Wu, Mingqiu; Johannes, Johannes; Radl, Stefan <br/> <br/>Abstract: In this paper, we study the liquid transport between particles of different sizes, as well as build a dynamic liquid bridge model to predict liquid transport between these two particles. Specifically, the drainage process of liquid adhering to two unequally-sized, non-porous wet particles is simulated using direct numerical simulations (DNS). Same as in our previous work (Wu et al., AIChE Journal, 2016, 62:1877–1897), we first provide an analytical solution of a proposed dynamic liquid bridge model. We find that such an analytical solution also describes liquid transport during collisions of unequally-sized particles very well. Finally, we show that our proposed model structure is sufficient to collapse all our direct numerical simulation data. Our model is hence able to predict liquid transport rates in size-polydisperse systems for a wide range of parameters http://hdl.handle.net/10993/39103 Title: Analysis of the cohesive zone behaviour through advanced multi-physics simulation technology <br/> <br/>Author, co-author: Baniasadi, Mehdi http://hdl.handle.net/10993/36963 Title: Presentation: "Mesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content" <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/36962 Title: Mesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus <br/> <br/>Abstract: Synthetic kitchen waste, produced on basis of a real kitchen waste, and two of its variations are studied. Previous study showed that the fermentation of kitchen waste was similar to the degradation of synthetic kitchen waste, further called model kitchen waste (MKW) with the same amounts of carbohydrates, fats and proteins. In this study the anaerobic degradation of this MKW (named MKW1; 23 % rapeseed oil) was investigated under mesophilic and thermophilic conditions at 2 different loadings. Additional experiments were performed with lower (MKW2; 14.7 %) and higher (MKW3; 27.2 %) rapeseed oil content at the expense of starch. An organic loading of 5 gVS/l leads to a fast and undisturbed degradation under mesophilic conditions. The volatile fatty acids (mainly acetic acid) appeared only during the first 3 days. Finally the amount of biogas been produced is weakly correlated with the oil content. Under thermophilic conditions the biogas production was retarded and the concentrations of the volatile fatty acids were generally higher whereas acetic acid was present for a period of 10 days. The final biogas amount was higher than compared to mesophilc conditions. At a higher loading of 25 gVS/l a strong retardation of biogas production was observed which correlates with very high concentrations of volatile fatty acids over the whole runtime period of 50 days. http://hdl.handle.net/10993/36723 Title: Two-Stage Process - a More Flexible Power Production of Biogas <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Benito Martin, Patricia Cristina; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/36722 Title: Vergleich der anaeroben Vergärung von realem und synthetischem Küchenabfall in Batchversuchen unterschiedlicher Beladung <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus <br/> <br/>Abstract: In the following article comparison between real kitchen waste and a synthetic kitchen waste is made. In total four experiments are discussed, all of them were conducted in batch mode at two different loadings: 25 and 5 goDM/l and two different temperatures: mesophilic and thermophilic. http://hdl.handle.net/10993/36652 Title: Präsentation: Vergleich der anaeroben Vergärung von realem und synthetischem Küchenabfall in Batchversuchen unterschiedlicher Beladung <br/> <br/>Author, co-author: Sobon-Muehlenbrock, Elena; Greger, Manfred; Schlienz, Markus http://hdl.handle.net/10993/35941 Title: Conversion analysis of a cylindrical biomass particle with a DEM-CFD coupling approach <br/> <br/>Author, co-author: Mohseni, Mohammad; Peters, Bernhard; Baniasadi, Mehdi http://hdl.handle.net/10993/34726 Title: Liquid Transport in Bi-disperse Particle Beds <br/> <br/>Author, co-author: Wu, Mingqiu; Khinast, Khinast; Radl, Stefan <br/> <br/>Abstract: Flow of highly saturated wet granular matter is encountered in wide range of engineering application, particularly in the pharmaceutics, food industry and energy sector , in addition, granular particles beds usually compose of various of particle properties (i.e.,, shape, size, density, etc.) and it well know that particle size polydispersity and shape significantly influence on the transport of mass and liquid in a fluidized bed system. http://hdl.handle.net/10993/34724 Title: A Model to Predict Liquid Bridge Formation Between Wet Particles Based on Direct Numerical Simulations <br/> <br/>Author, co-author: Wu, Mingqiu; Khinast, Johannes; Radl, Stefan <br/> <br/>Abstract: We study dynamic liquid bridge formation, which is relevant for wet granular flows involving highly viscous liquids and short collisions. Specifically, the drainage process of liquid adhering to two identical, non-porous wet particles with different initial film heights is simulated using Direct Numerical Simulations (DNS). We extract the position of the interface, and define the liquid bridge and its volume by detecting a characteristic neck position. This allows us building a dynamic model for predicting bridge volume, and the liquid remaining on the particle surface. Our model is based on two dimensionless mobility parameters, as well as a dimensionless time scale to describe the filling process. In the present work model parameters were calibrated with DNS data. We find that the proposed model structure is sufficient to collapse all our simulation data, indicating that our model is general enough to describe liquid bridge formation between equally sized particles http://hdl.handle.net/10993/34600 Title: The effect of liquid bridge model details on the dynamics of wet fluidized beds <br/> <br/>Author, co-author: Wu, Mingqiu; Khinast, Johannes; Radl, Stefan <br/> <br/>Abstract: Wet fluidized beds of particles in small periodic domains are simulated using the CFD-DEM approach. A liquid bridge is formed upon particle-particle collisions, which then ruptures when the particle separation exceeds a critical distance. The simulations take into account both surface tension and viscous forces due to the liquid bridge. We perform a series of simulations based on different liquid bridge formation models: (1) the static bridge model of Shi and McCarthy, (2) a simple static version of the model of Wu et al., as well as (3) the full dynamic bridge model of Wu et al. We systematically compare the differences caused by different liquid bridge formation models, as well as their sensitivity to system parameters. Finally, we provide recommendations for which systems a dynamic liquid bridge model must be used, and for which application this appears to be less important http://hdl.handle.net/10993/33794 Title: A novel optimization approach to estimating kinetic parameters of the enzymatic hydrolysis of corn stover <br/> <br/>Author, co-author: Qi, Fenglei; Wright, Mark http://hdl.handle.net/10993/33791 Title: An Integral Approach to Multi-physics Application for Packed Bed Reactors <br/> <br/>Author, co-author: Peters, Bernhard; Besseron, Xavier; Estupinan, A.; Hoffmann, F.; Michael, M.; Mahmoudi, Amir Houshang; Mohseni, M. http://hdl.handle.net/10993/33783 Title: Coupled CFD-DEM with Heat and Mass transfer to Investigate the Melting of a Granular Packed Bed <br/> <br/>Author, co-author: Baniasadi, Mehdi; Baniasadi, Maryam; Peters, Bernhard <br/> <br/>Abstract: The eXtended Discrete Element Method (XDEM) platform which is a Coupled Eulerian-Lagrangian framework with heat and mass transfer, is extended for melting of granular packed beds. In this method, the fluid is simulated by computational fluid dynamics (CFD) and the soft-sphere discrete element approach (DEM) is used for the particle system. A four-way coupling accounts for solid-liquid interaction via drag and buoyancy forces and the collisions between the particles and the walls. The contact forces between the particles and wall-particle contacts have been calculated by the hertz-mindlin model. The particles heat up, melt and shrink due to heat and mass exchange, and the temperature distributions inside the particles are described. In order to validate the method, melting of a single ice particle and of a packed bed of ice in flowing water have been carried out. Very good agreement between the simulation and experiment has been achieved. The effects of the temperature and velocity of flowing water on melting rate are also discussed.