The Conceptual Design of a Perfusion Reactor Using a Complexity Measure

2008 ◽  
Author(s):  
Andreas Bischof ◽  
Jorge Angeles ◽  
Lucienne Blessing
Keyword(s):  
Mathematical Model ◽  
Porous Medium ◽  
Dynamical Systems ◽  
Simple Model ◽  
Conceptual Design ◽  
Living Cells ◽  
Complexity Measure ◽  
Ceramic Foam ◽  
Cell Life ◽  
The Subject

The conceptual design of a perfusion reactor is the subject of this paper. The main objective of the reactor is the provision of nutrients to living cells grown in a porous medium fabricated of a given ceramic foam. In order to increase reactor throughput, the nutrients should be provided in a minimum time, without affecting the cell life. Various layouts of identical ceramic-foam pieces hosting the cells are proposed, the purpose being to select the variant with the highest likelihood of optimum performance, in the absence of a detailed mathematical model. A simple model is proposed, drawn from the discipline of hydraulic dynamical systems, which leads to a flow-complexity measure. The variant with the lowest complexity is then selected, for which a possible embodiment is proposed.

scholarly journals Concepts and new perspectives for long span bridges

2016 ◽  
Vol 5 (1) ◽  
pp. 75-97
Author(s):  
Fabio Brancaleoni
Keyword(s):  
Conceptual Design ◽  
Present State ◽  
Critical Parameter ◽  
State Of The Art ◽  
Span Length ◽  
Factors Affecting ◽  
Long Span Bridges ◽  
Future Developments ◽  
Long Span ◽  
The Subject

AbstractA discussion of the dominant factors affecting the behaviour of long span cable supported bridges is the subject of this paper. The main issue is the evolution of properties and response of the bridge with the size of the structure, represented by the critical parameter of span length, showing how this affects the conceptual design. After a review of the present state of the art, perspectives for future developments are discussed.

scholarly journals Cytological studies on the viruses of fowl-pox and vaccinia

1928 ◽  
Vol 102 (719) ◽  
pp. 406-418 ◽  
Keyword(s):  
Life Cycle ◽  
Infected Cell ◽  
Living Cells ◽  
Histological Technique ◽  
The Subject ◽  
Nuclear Structures ◽  
Source Of Error

Although, as is well known, the ultra-microscopic viruses are invisible in histological preparations, yet characteristic bodies occur within certain of the cells of animals infected with such organisms. The origin and nature of these so-called “virus bodies” has been the subject of much controversy. By some they have been regarded as the actual parasite, or at least as phases in its life cycle. To von Prowazek they were dual in character consisting of microorganisms embedded in material produced by the reaction of the cytoplasm of the infected cell. Still other observers regarded such bodies as products of cellular disintegration. In a former paper (Findlay and Ludford (1926)) we have referred to the various views held by writers in this field and have made a survey of the literature of the subject in the form of a pictographic review. We shall, therefore, only mention previous work in this field, in so far as it directly concerns our personal observations. A conspicuous fault of much of the earlier work has been the unsatisfactory histological technique employed, especially the nature of the fixative. The earlier cytological work was carried out with fixatives, which although satisfactory for the subsequent demonstration of nuclear structures were very destructive to the cytoplasm. This is particularly unfortunate since most of the virus bodies occur in the ground cytoplasm of cells. We have endeavoured to rectify this source of error in our work by employing fixatives, which have been proved to fix the cells in such a manner as to give an appearance as nearly as possible identical with their structure, as seen in the living cells.

Dynamic Analysis of a Three-Dimensional Poroelastic Beam Using the Boundary-Element Method

2018 ◽  
Vol 769 ◽  
pp. 329-335
Author(s):  
Andrey Petrov ◽  
Leonid A. Igumnov
Keyword(s):  
Mathematical Model ◽  
Porous Medium ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Three Dimensional ◽  
Element Solution ◽  
Harmonic Force ◽  
Porosity And Permeability ◽  
Beam Thickness ◽  
Element Method

The problem of the effect of a normal harmonic force on a porous beam in a 3D formulation is solved using the boundary-element method. A homogeneous fully saturated elastic porous medium is described using Biot’s mathematical model. The effect of the porosity and permeability parameters on the deflection of the beam and the distribution of pore pressure over the beam thickness is investigated. The comparison of the boundary-element solution with a 2D numerical-analytical one is given.

Self-Excited Oscillations in Dynamical Systems Possessing Retarded Actions

1942 ◽  
Vol 9 (2) ◽  
pp. A65-A71 ◽  
Author(s):  
Nicholas Minorsky
Keyword(s):  
Differential Equation ◽  
Dynamical Systems ◽  
Differential Equations ◽  
Linear Equation ◽  
Finite Order ◽  
Characteristic Equation ◽  
High Derivative ◽  
Time Lags ◽  
Constant Coefficients ◽  
The Subject

Abstract There exists a variety of dynamical systems, possessing retarded actions, which are not entirely describable in terms of differential equations of a finite order. The differential equations of such systems are sometimes designated as hysterodifferential equations. An important particular case of such equations, encountered in practice, is when the original differential equation for unretarded quantities is a linear equation with constant coefficients and the time lags are constant. The characteristic equation, corresponding to the hysterodifferential equation for retarded quantities in such a case, has a series of subsequent high-derivative terms which generally converge. It is possible to develop a simple graphical interpretation for this equation. Such systems with retarded actions are capable of self-excitation. Self-excited oscillations of this character are generally undesirable in practice and it is to this phase of the subject that the present paper is devoted.

scholarly journals Numerical Simulation of a New Porous Medium Burner with Two Sections and Double Decks

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 185 ◽  
Author(s):  
Zhenzhen Jia ◽  
Qing Ye ◽  
Haizhen Wang ◽  
He Li ◽  
Shiliang Shi
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Porous Medium ◽  
Industrial Development ◽  
High Efficiency ◽  
Methane Combustion ◽  
Combustion Mechanism ◽  
Gas Mixture ◽  
Temperature And Pressure ◽  
Save Energy

Porous medium burners are characterized by high efficiency and good stability. In this study, a new burner was proposed based on the combustion mechanism of the methane-air mixture in the porous medium and the preheating effect. The new burner is a two-section and double-deck porous medium with gas inlets at both ends. A mathematical model for the gas mixture combustion in the porous medium was established. The combustion performance of the burner was simulated under different equivalence ratios and inlet velocities of premixed gas. The methane combustion degree, as well as the temperature and pressure distribution, was estimated. In addition, the concentrations of emissions of NOx for different equivalence ratios were investigated. The results show that the new burner can not only realize sufficient combustion but also save energy. Furthermore, the emission concentration of NOx is very low. This study provides new insights into the industrial development and application of porous medium combustion devices.

Transitioning from a Traditional Classroom to the Online Environment

2011 ◽  
pp. 126-134
Author(s):  
Barbara Wilmes ◽  
Stephanie Huffman ◽  
Wendy Rickman
Keyword(s):  
Simple Model ◽  
Online Teaching ◽  
Transition Period ◽  
Traditional Classroom ◽  
Planning Model ◽  
Technology Planning ◽  
The Subject ◽  
Technology Strategies ◽  
Faculty And Administrators ◽  
Student Instructor

This chapter will focus on how faculty can effectively determine their technological needs as they move from the traditional classroom to an online teaching environment through strategic planning. SIMPLE is a technology planning model, which can be used by faculty and administrators to stair-step themselves through this transition period. SIMPLE is an acronym representing six areas which should be addressed when developing and implementing technology strategies – 1) student/instructor assessment, 2) inventory, 3) measurement, 4) planning, 5) leadership, and 6) evaluation. These six components represent common threads throughout the literature on the subject of technology planning, which were utilized to develop the SIMPLE model, and can be easily utilized to guide faculty.

Crystal structures and snapshots along the reaction pathway of human phosphoserine phosphatase

2019 ◽  
Vol 75 (6) ◽  
pp. 592-604 ◽  
Author(s):  
Marie Haufroid ◽  
Manon Mirgaux ◽  
Laurence Leherte ◽  
Johan Wouters
Keyword(s):  
Molecular Dynamics ◽  
Reaction Mechanism ◽  
Crystal Structures ◽  
Reaction Pathway ◽  
Living Cells ◽  
Homocysteic Acid ◽  
Phosphoserine Phosphatase ◽  
Key Enzyme ◽  
The Subject ◽  
Dynamics Simulations

The equilibrium between phosphorylation and dephosphorylation is one of the most important processes that takes place in living cells. Human phosphoserine phosphatase (hPSP) is a key enzyme in the production of serine by the dephosphorylation of phospho-L-serine. It is directly involved in the biosynthesis of other important metabolites such as glycine and D-serine (a neuromodulator). hPSP is involved in the survival mechanism of cancer cells and has recently been found to be an essential biomarker. Here, three new high-resolution crystal structures of hPSP (1.5–2.0 Å) in complexes with phosphoserine and with serine, which are the substrate and the product of the reaction, respectively, and in complex with a noncleavable substrate analogue (homocysteic acid) are presented. New types of interactions take place between the enzyme and its ligands. Moreover, the loop involved in the open/closed state of the enzyme is fully refined in a totally unfolded conformation. This loop is further studied through molecular-dynamics simulations. Finally, all of these analyses allow a more complete reaction mechanism for this enzyme to be proposed which is consistent with previous publications on the subject.

The dynamics of language

1999 ◽  
Vol 22 (2) ◽  
pp. 284-285
Author(s):  
Peter W. Culicover ◽  
Andrzej Nowak
Keyword(s):  
Phase Space ◽  
Dynamical Systems ◽  
Simple Model ◽  
Syntactic Structure ◽  
Neural Assemblies ◽  
Systems Perspective ◽  
Model Based ◽  
Associative Structures

To deal with syntactic structure, one needs to go beyond a simple model based on associative structures, and to adopt a dynamical systems perspective, where each phrase and sentence of a language is represented as a trajectory in a syntactic phase space. Neural assemblies could possibly be used to produce dynamics that in principle could handle syntax along these lines.

The effect of hydrodynamic dispersion on reactive flows in porous media

2001 ◽  
Vol 12 (5) ◽  
pp. 557-569 ◽  
Author(s):  
J. CHADAM ◽  
P. ORTOLEVA ◽  
Y. QIN ◽  
R. STAMICAR
Keyword(s):  
Mathematical Model ◽  
Porous Medium ◽  
Critical Value ◽  
Reactive Flow ◽  
Hydrodynamic Dispersion ◽  
Reaction Interface ◽  
Shape Stability ◽  
Linearized Problem ◽  
New Feature ◽  
Moving Free Boundary

The shape stability of the reaction interface for reactive flow in a porous medium is investigated. Previous work showed that the Reaction-Infiltration Instability could cause the reaction zone to lose stability when the Peclet number exceeded a critical value. The new feature of this study is to include a velocity-dependent hydrodynamic dispersion. A mathematical model for this phenomenon is given in the form of a moving free-boundary problem. The spectrum of the linearized problem is obtained, and the related analysis and numerical calculations show that the onset of the instability is not eliminated by the new dispersive terms. The details of analysis show that the instability is reduced especially by the transverse dispersion.

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