scholarly journals Multi-Scale Modeling of the Dynamics of a Fibrous Reactor: Use of an Analytical Solution at the Micro-Scale to Avoid the Spatial Discretization of the Intra-Fiber Space

Fluids ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 3 ◽  
Author(s):  
Adam Dobri ◽  
Thanasis D. Papathanasiou
Keyword(s):  
Hybrid Model ◽  
Heterogeneous Systems ◽  
Model Systems ◽  
Bulk Liquid ◽  
Fiber Space ◽  
Micro Scale ◽  
Macro Scale ◽  
Direct Numerical Solution ◽  
Parametric Analyses ◽  
Dependent Transport

Direct modeling of time-dependent transport and reactions in realistic heterogeneous systems, in a manner that considers the evolution of the quantities of interest in both, the macro-scale (suspending fluid) and the micro-scale (suspended particles), is currently well beyond the capabilities of modern supercomputing. This is understandable, since even a simple system such as this can easily contain over 107 particles, whose length and time scales differ from those of the macro-scale by several orders of magnitude. While much can be gained by applying direct numerical solution to representative model systems, the direct approach is impractical when the performance of large, realistic systems is to be modeled. In this study we derive and analyze a “hybrid” model that is suitable for fibrous reactors. The model considers convection/diffusion in the bulk liquid, as well as intra-fiber diffusion and reaction. The essence of our approach is that diffusion and (first-order) reaction in the intra-fiber space are handled semi-analytically, based on well-established theory. As a result, the problem of intra-fiber transport and reaction is reduced to an easily solvable set of n 0 ODEs, where n 0 is the number of terms in the Bessel expansion evaluated without recourse to approximation; this set is coupled, point-wise, with a numerical model of the macro-scale. When the latter is discretized using N nodes, the total “hybrid” model for the system consists of a system of N ( 2 + n 0 ) ODEs, which is easily solvable on a modest workstation. Parametric analyses are presented and discussed.

Contact characteristic analysis of spindle–toolholder joint at high speeds based on the fractal model

2016 ◽  
Vol 231 (5) ◽  
pp. 1025-1036 ◽  
Author(s):  
Yongsheng Zhao ◽  
Jingjing Xu ◽  
Ligang Cai ◽  
Weimin Shi ◽  
Zhifeng Liu ◽  
...  
Keyword(s):  
Finite Element ◽  
Hybrid Model ◽  
Contact Stiffness ◽  
Element Model ◽  
Fractal Model ◽  
Contact Ratio ◽  
Characteristic Analysis ◽  
Micro Scale ◽  
High Speeds ◽  
Macro Scale

Due to the influence of centrifugal force, accurate contact stiffness model of spindle–toolholder joint at high speeds is crucial in predicting the dynamic behavior and chatter vibration of spindle–toolholder system. In this paper, a macro–micro scale hybrid model is presented to obtain the contact stiffness of spindle–toolholder joint in high speeds. The hybrid model refers to the finite element model in macro-scale and three-dimensional fractal model in micro-scale. The taper contact surface of spindle–toolholder joint is assumed flat in macro-scale and the finite element method is used to obtain the pressure distribution at different speeds. In micro-scale, the topography of contact surfaces is fractal featured and determined by fractal parameters. Asperities in micro-scale are considered as elastic and plastic deformation. Then, the contact ratio, radial and torsional contact stiffness of spindle–toolholder joint can be calculated by integrating the micro asperities. Experiments with BT40 type toolholder–spindle assembly are conducted to verify the proposed model in the case of no speed. The reasonable intervals of spindle speed and drawbar force can be obtained based on the presented hybrid model, which will provide theoretical basis for the application and optimization of the spindle–toolholder system.

Noninvasive Continuous Monitoring of Adipocyte Differentiation: From Macro to Micro Scales

2019 ◽  
Vol 25 (1) ◽  
pp. 119-128 ◽  
Author(s):  
Maayan Lustig ◽  
Qingling Feng ◽  
Yohan Payan ◽  
Amit Gefen ◽  
Dafna Benayahu
Keyword(s):  
Continuous Monitoring ◽  
Model Systems ◽  
Image Processing Algorithm ◽  
Micro Scale ◽  
Obesity And Diabetes ◽  
Macro Scale ◽  
Percentage Area ◽  
Novel Method ◽  
The Mean ◽  
Morphological Differences

Abstract3T3-L1 cells serve as model systems for studying adipogenesis and research of adipose tissue-related diseases, e.g. obesity and diabetes. Here, we present two novel and complementary nondestructive methods for adipogenesis analysis of living cells which facilitate continuous monitoring of the same culture over extended periods of time, and are applied in parallel at the macro- and micro-scales. At the macro-scale, we developed visual differences mapping (VDM), a novel method which allows to determine level of adipogenesis (LOA)—a numerical index which quantitatively describes the extent of differentiation in the whole culture, and percentage area populated by adipocytes (PAPBA) across a whole culture, based on the apparent morphological differences between preadipocytes and adipocytes. At the micro-scale, we developed an improved version of our previously published image-processing algorithm, which now provides data regarding single-cell morphology and lipid contents. Both methods were applied here synergistically for measuring differentiation levels in cultures over multiple weeks. VDM revealed that the mean LOA value reached 1.11 ± 0.06 and the mean PAPBA value reached >60%. Micro-scale analysis revealed that during differentiation, the cells transformed from a fibroblast-like shape to a circular shape with a build-up of lipid droplets. We predict a vast potential for implementation of these methods in adipose-related pharmacological research, such as in metabolic-syndrome studies.

Microtubule Dynamics and Organelle Transport in Reticulomyxa

1990 ◽  
Vol 48 (3) ◽  
pp. 194-195
Author(s):  
Yih-Tai Chen ◽  
Ursula Euteneuer ◽  
Ken B. Johnson ◽  
Michael P. Koonce ◽  
Manfred Schliwa
Keyword(s):  
Plasma Membrane ◽  
Light Microscopy ◽  
Cytoplasmic Dynein ◽  
Living Cells ◽  
Microtubule Dynamics ◽  
Model Systems ◽  
Organelle Transport ◽  
Biochemical Characteristics ◽  
Dependent Transport

The application of video techniques to light microscopy and the development of motility assays in reactivated or reconstituted model systems rapidly advanced our understanding of the mechanism of organelle transport and microtubule dynamics in living cells. Two microtubule-based motors have been identified that are good candidates for motors that drive organelle transport: kinesin, a plus end-directed motor, and cytoplasmic dynein, which is minus end-directed. However, the evidence that they do in fact function as organelle motors is still indirect.We are studying microtubule-dependent transport and dynamics in the giant amoeba, Reticulomyxa. This cell extends filamentous strands backed by an extensive array of microtubules along which organelles move bidirectionally at up to 20 μm/sec (Fig. 1). Following removal of the plasma membrane with a mild detergent, organelle transport can be reactivated by the addition of ATP (1). The physiological, pharmacological and biochemical characteristics show the motor to be a cytoplasmic form of dynein (2).

scholarly journals 2D-wavelet based micro and macro texture analysis for asphalt pavement under snow or ice condition

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Feng Li ◽  
Gulnigar Ablat ◽  
Siqi Zhou ◽  
Yixin Liu ◽  
Yufeng Bi ◽  
...  
Keyword(s):  
Wavelet Transform ◽  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Micro Scale ◽  
Braking System ◽  
Macro Scale ◽  
Texture Characteristics ◽  
The Mean ◽  
Resistance Performance

AbstractIn ice and snow weather, the surface texture characteristics of asphalt pavement change, which will significantly affect the skid resistance performance of asphalt pavement. In this study, five asphalt mixture types of AC-5, AC-13, AC-16, SMA-13, SMA-16 were prepared under three conditions of the original state, ice and snow. In this paper, a 2D-wavelet transform approach is proposed to characterize the micro and macro texture of pavement. The Normalized Energy (NE) is proposed to describe the pavement texture quantitatively. Compared with the mean texture depth (MTD), NE has the advantages of full coverage, full automation and wide analytical scale. The results show that snow increases the micro-scale texture because of its fluffiness, while the formation of the ice sheets on the surface reduces the micro-scale texture. The filling effect of snow and ice reduces the macro-scale texture of the pavement surface. In a follow-up study, the 2D-wavelet transform approach can be applied to improve the intelligent driving braking system, which can provide pavement texture information for the safe braking strategy of driverless vehicles.

Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

2006 ◽  
Vol 12 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Keisuke Suzuki ◽  
Takashi Ikegami
Keyword(s):  
Pattern Formation ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Spiral Structure ◽  
Scale Interactions ◽  
Micro Scale ◽  
Macro Scale ◽  
Loop Network ◽  
Spatial Pattern Formation

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

scholarly journals Experimental study of the effects of wire EDM on the characteristics of ferritic steel, at a micro-scale on the contour cut surface

2018 ◽  
Vol 115 (4) ◽  
pp. 413
Author(s):  
Nida Naveed
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Surface Characteristics ◽  
Surface Damage ◽  
Cutting Process ◽  
Contour Method ◽  
X Ray Diffraction ◽  
Micro Scale ◽  
Macro Scale ◽  
Cut Surface

This study, on a micro-scale, of the WEDM cut surfaces of specimens to which the contour method of residual stress measurement is being applied provides detailed information about the effects of the cutting process on the surface quality. This is defined by a combination of several parameters: variation in surface contour profile, sub-surface damage and surface texture. Measurements were taken at the start, the middle and at the end of the cut. This study shows that during WEDM cutting, a thin layer, extending to a depth of a few micrometres below the surface of the cut, is transformed. This layer is known as the recast layer. Using controlled-depth etching and X-ray diffraction, it is shown that this induces an additional tensile residual stress, parallel to the plane of the cut surface. The WEDM cut surface and sub-surface characteristics are also shown to vary along the length of the cut. Moreover, these micro-scale changes were compared with macro-scale residual stress results and provides an indication of the point at which the changes occurred by cutting process can be significantly relative to the macro-scale residual stress in a specimen.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

A SIZE EFFECT STUDY ON THE SPLITTING CRACK INITIATION AND PROPAGATION IN OFF-AXIS LAYERS OF COMPOSITE LAMINATES

2021 ◽  
Author(s):  
YAO QIAO ◽  
QIWEI ZHANG ◽  
TROY NAKAGAWA ◽  
MARCO SALVIATO
Keyword(s):  
Crack Initiation ◽  
Size Effect ◽  
Fiber Reinforced Polymers ◽  
Structural Behavior ◽  
Crack Initiation And Propagation ◽  
Damage Mechanisms ◽  
Micro Scale ◽  
Morphological Studies ◽  
Initiation And Propagation ◽  
Macro Scale

This work proposes an investigation on size effects in micro-scale splitting crack initiation and propagation and their consequences on the macro-scale structural behavior carbon-fiber reinforced polymers under transverse tension. Towards this goal, size effect tests were experimentally conducted on both notch-free [90]n composites and specimens with different notch types under three-point bending. The mechanical tests were followed by morphological studies to identify the micro-scale damage mechanisms and their evolution. The results clearly show that splitting crack initiation in the transverse direction of composites not only happens at the fiber/matrix interface but also in the matrix. Moreover, the subsequent development of these damage mechanisms can depend on the structure size. This interesting phenomenon inherently leads to size-dependent structural behavior which can be described through Baznt’s Size Effect Laws. This study on the splitting crack initiation and propagation can provide unprecedented information for the calibration and validation of micromechanical models for the damage behavior of fiber composites at the microscale.

Generation and Enforcement of Process-Driven Manufacturability Constraints: A Survey of Methods and Perspectives for Product Design

2021 ◽  
pp. 1-33
Author(s):  
Albert Patterson ◽  
Yong Hoon Lee ◽  
James T. Allison
Keyword(s):  
General Solution ◽  
Design For Manufacturing ◽  
Top Down ◽  
Specific Process ◽  
Micro Scale ◽  
Component Design ◽  
Macro Scale ◽  
Simple Mass ◽  
Common Problems ◽  
Scale Design

Abstract Design-for-manufacturing (DFM) concepts have traditionally focused on design simplification; this is highly effective for relatively simple, mass-produced products, but tends to be too restrictive for more complex designs. Effort in recent decades has focused on creating methods for generating and imposing specific, process-derived technical manufacturability constraints for some common problems. This paper presents an overview of the problem and its design implications, a discussion of the nature of the manufacturability constraints, and a survey of the existing approaches and methods for generating/enforcing the minimally-restrictive manufacturability constraints within several design domains. Five major design perspectives or viewpoints were included in the study, including the system design (top-down), product/component design (bottom-up), the manufacturing process-dominant case (product/component design under a specific process), the part-redesign perspective, and sustainability perspective. Manufacturability constraints within four design levels or scales were explored as well, ranging from macro-scale to sub-micro-scale design. Very little previous work was found in many areas, but it is clear from the existing literature that the problem and a general solution to it are very important to explore further in future DFM efforts.

Micro-scale tearing mode turbulence in the diffusion region during macro-scale evolution of turbulent reconnection

2021 ◽  
Author(s):  
Takuma Nakamura ◽  
Hiroshi Hasegawa ◽  
Tai Phan ◽  
Kevin Genestreti ◽  
Richard Denton ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Conversion ◽  
Magnetic Reconnection ◽  
Diffusion Region ◽  
Electron Diffusion ◽  
Efficient Energy ◽  
Micro Scale ◽  
Island Evolution ◽  
Macro Scale ◽  
Scale Evolution

<p>Magnetic reconnection is a key fundamental process in collisionless plasmas that explosively converts magnetic energy to plasma kinetic and thermal energies through a change of magnetic field topology in an electron-scale central region called the electron diffusion region. Past simulations and observations demonstrated that this process causes efficient energy conversion through the formation of multiple macro-scale or micro-scale magnetic islands/flux ropes. However, how these different spatiotemporal scale phenomena are coupled is still poorly understood. In this study, to investigate the turbulent evolution of magnetic reconnection, we perform a new large-scale fully kinetic simulation of a thin current sheet considering a power-law spectrum of initial fluctuations in the magnetic field as frequently observed in the Earth’s magnetotail. The simulation demonstrates that during a macro-scale evolution of turbulent reconnection, the merging of macro-scale islands results in reduction of the rate of reconnection as well as the aspect ratio of the electron diffusion region. This allows the repeated, quick formation of new electron-scale islands within the electron diffusion region, leading to an efficient energy cascade between macro- and micro-scales. The simulation also demonstrates that a strong electron acceleration/heating occurs during the micro-scale island evolution within the EDR. These new findings indicate the importance of non-steady features of the EDR to comprehensively understand the energy conversion and cascade processes in collisionless reconnection.</p>

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