Photobioreactor Stability by Phase Plane Technique Applied to Spirulina Maxima Growth

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Khaled Belkacemi ◽  
Safia Hamoudi
Keyword(s):  
Steady State ◽  
Phase Plane ◽  
Biologically Active ◽  
Raw Material ◽  
System Stability ◽  
Stable Steady State ◽  
Monod Kinetics ◽  
Spirulina Maxima ◽  
Plane Technique ◽  
The Stability

Spirulina maxima is a worthy multicellular filamentous micro-algae used as a food supplement and raw material for fine chemicals and biologically active compounds production. Intensive approach consisting of cultivating pure strains of this photoautotroph microorganism in photobioreactors is more desirable than extensive ones, largely incontrollable with regard to production stability. Determining the best reaction conditions to reach a steady state in the runway events is often needed in biological systems. For a biochemical engineer, knowing the system stability for an optimal bioreactor configuration is crucial to estimate the rate at which dependent variables grow or decay with the time reaction. The stability analysis becomes important in recycle processes in which possibility that these systems influence themselves exists. The aim of this work deals with the 1) description of the growth kinetics by a logistic and unstructured model based on Monod kinetics taking into account the maintenance in life of viable cells; 2) establishment of a dynamic growth model for Spirulina maxima cultivated in continuous lamellar photobioreactors using industrial manures as macro-nutrients; 3) determination of optimal culture conditions sustaining a stable growth of S. maxima in a system of two bioreactors in series; and 4) investigation of the dynamic stability of this multivariable system with nonlinear dynamics using phase plane technique (PPT). Although good mixing of the culture is essential for ensuring adequate supply of nutrients and prevention of the accumulation of toxic metabolites. Excessive agitation causes mechanical damage to Spirulina cells. An air flow rate of 2.5 L/min for airlift agitation represented a balance between the need to provide good mixing and to avoid cell damage. A stable steady state was achieved corresponding to a productivity of 10.8 g. m2/day when the system was supplied with 0.2 g N/L of minerals, at a dilution rate of 0.1 1/day, temperature of 30 °C under light intensity of 18 Klux. PPT as a powerful procedure successfully predicts the stability of such a complex system very well.

scholarly journals Suppression of marine ice sheet instability

2018 ◽  
Vol 857 ◽  
pp. 648-680 ◽  
Author(s):  
Samuel S. Pegler
Keyword(s):  
Steady State ◽  
Rapid Assessment ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stable Steady State ◽  
Ice Shelf ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
The Stability

A long-standing open question in glaciology concerns the propensity for ice sheets that lie predominantly submerged in the ocean (marine ice sheets) to destabilise under buoyancy. This paper addresses the processes by which a buoyancy-driven mechanism for the retreat and ultimate collapse of such ice sheets – the marine ice sheet instability – is suppressed by lateral stresses acting on its floating component (the ice shelf). The key results are to demonstrate the transition between a mode of stable (easily reversible) retreat along a stable steady-state branch created by ice-shelf buttressing to tipped (almost irreversible) retreat across a critical parametric threshold. The conditions for triggering tipped retreat can be controlled by the calving position and other properties of the ice-shelf profile and can be largely independent of basal stress, in contrast to principles established from studies of unbuttressed grounding-line dynamics. The stability and recovery conditions introduced by lateral stresses are analysed by developing a method of constructing grounding-line stability (bifurcation) diagrams, which provide a rapid assessment of the steady-state positions, their natures and the conditions for secondary grounding, giving clear visualisations of global stabilisation conditions. A further result is to reveal the possibility of a third structural component of a marine ice sheet that lies intermediate to the fully grounded and floating components. The region forms an extended grounding area in which the ice sheet lies very close to flotation, and there is no clearly distinguished grounding line. The formation of this region generates an upsurge in buttressing that provides the most feasible mechanism for reversal of a tipped grounding line. The results of this paper provide conceptual insight into the phenomena controlling the stability of the West Antarctic Ice Sheet, the collapse of which has the potential to dominate future contributions to global sea-level rise.

scholarly journals Desain dan analisis pengaruh parameter PI dan variasi kecepatan pada respon sistem kontrol arah hadap prototype kendaraan listrik

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Afif Caesar Distara ◽  
Fatkhur Rohman
Keyword(s):  
Control System ◽  
Steady State ◽  
Electric Vehicles ◽  
Rise Time ◽  
Small Error ◽  
Settling Time ◽  
System Stability ◽  
Prototype System ◽  
Stability Parameters ◽  
The Stability

Electric vehicles are alternative vehicles that carry energy efficient. At this time the dominant vehicle uses ordinary wheels so that it will become an obstacle in the maneuver function that requires movement in various directions. With mechanum wheels the vehicle can move in various directions by adjusting the direction of rotation of each wheel. The problem is choosing the right control system for the control system needed by the vehicle. The purpose of this study is to determine and analyze the effect of variations in the value of PI (Proportional Integral) and speed of the vehicle to the stability response of the system to control the direction of prototype electric vehicles. This study method is an experiment that is by giving a treatment, then evaluating the effects caused by the research object. The results of this study can be concluded that the variation of PI constant values and speed variations have an effect on the stability parameters of the system, namely rise time, settling time, overshot, and steady state error. To get the best system stability response results can use the constant value PI Kp = 2; and Ki = 17; where the stability response of the system for direction control at each speed condition has a fairly good value with a fast rise time, fast settling time, small overshot and a small error steady state compared to other PI constant values in this study.Keywords: mechanum wheel, PI control, direction, prototype, system stability

Frequency-domain analysis method for analyzing and improving the steady-state characteristics of microcantilever in tapping-mode atomic force microscopy

2018 ◽  
Vol 82 (1) ◽  
pp. 10701
Author(s):  
Xiaohui Gu ◽  
Lining Sun ◽  
Changhai Ru
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Stability Margin ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
System Stability ◽  
Analysis Method ◽  
External Interference ◽  
Tapping Mode ◽  
The Stability

In tapping-mode AFM, the steady-state characteristics of microcantilever are extremely important to determine the AFM performance. Due to the external excitation signal and the tip-sample interactions, the solving process of microcantilever motion equation will become very complicated with the traditional time-domain analysis method. In this paper, we propose the novel frequency-domain analysis method to analyze and improve the steady-state characteristics of microcantilever. Compared with the previous methods, this new method has three prominent advantages. Firstly, the analytical expressions of amplitude and phase of cantilever system can be derived conveniently. Secondly, the stability of the cantilever system can be accurately determined and the stability margin can be obtained quantitatively in terms of the phase margin and the magnitude margin. Thirdly, on this basis, external control mechanism can be devised quickly and easily to guarantee the high stability of the cantilever system. With this novel method, we derive the frequency response curves and discuss the great influence of the intrinsic parameters on the system stability, which provides theoretical guidance for selecting samples to achieve better AFM images in the experiments. Moreover, we introduce a new external series correction method to significantly increase the stability margin. The results indicate that the cantilever system is no longer easily disturbed by external interference signals.

Chaotic Behavior of a Two Mass Bouncing System

1992 ◽  
Author(s):  
Chi-Wook Lee ◽  
Ali Seireg ◽  
Joseph Duffy
Keyword(s):  
Power Spectrum ◽  
Spectrum Analysis ◽  
Phase Plane ◽  
Chaotic Behavior ◽  
Power Spectrum Analysis ◽  
Ground Contact ◽  
Hopping Robots ◽  
Plane Technique ◽  
The Stability ◽  
Spring Constants

Abstract This study investigates the behavior of simple two mass bouncing systems which are released from a certain height. A nonlinearity exists in the discontinuity of the flight and the ground modes, although the behavior of the systems is linear in each mode. Such oscillators provide models for mechanical systems such as legged systems for hopping robots. The phase plane technique and the power spectrum analysis are used to investigate the stability of bouncing systems and the chaos that may occur. The effects of the spring constants and the damping coefficient at the ground contact on the bouncing behavior is also investigated.

Chaotic Characteristic Analysis of Concrete Fracture System Based on Lyapunov Exponent Stability Criterion

2013 ◽  
Vol 423-426 ◽  
pp. 1105-1109
Author(s):  
Jun Wei Song
Keyword(s):  
Compressive Strength ◽  
Steady State ◽  
Stability Criterion ◽  
System Stability ◽  
Stress System ◽  
Characteristic Analysis ◽  
Chaotic State ◽  
Whole Process ◽  
Strain Stress ◽  
The Stability

According to the research on whole curves of strain-stress of concrete materials, the paper illustrates in evidence features of stages and shows that the discrete feature of curve often occurs in strain-softening stage. After chaotic dynamic analysis of testing datas, it presents that system of whole process of strain-stress evolves from ordered steady state to low chaotic state and then to high chaotic state along with increase of compressive strength. The linear relationship of strain-stress grows evident and the system evolves from strong ordered steady state to low chaos state. The strain-stress system before compressive strength peak is basically in weak chaotic state. Theis proposed to be the stability criterion of concrete features in different stress stages, and the is regarded as the representative value of the system stability degree. The calculation of example shows that the stability criterion definited by the proposed method is consistent with the actural situation.

An Online Adaptive Fast Control Approach Based on Local Linearization and Its Application to a Large Inertia System

2011 ◽  
Author(s):  
Jia Xie ◽  
Shengdun Zhao ◽  
Zhenghui Sha ◽  
Jintao Liang
Keyword(s):  
Steady State ◽  
Control Process ◽  
Transition Process ◽  
Hybrid Structure ◽  
Raw Material ◽  
Stable Steady State ◽  
Small Range ◽  
Control Approach ◽  
Local Linearization ◽  
Fast Control

In this paper, an online adaptive fast control approach (OAFC) based on local linearization is proposed. This engineering approach has two distinctive features: a) it can realize stable steady-state control; and b) it can make the transition control process fast and smooth. It applies a hybrid structure system and uses the local linearization in a small range of the error to solve the control problem caused by the nonlinear, time-varying, and time-delay large inertia system involved in this paper. Firstly, by timely decoupling the transition process and the steady state, the time of the transition process is reduced. Then, OAFC is realized by proposed OAFC algorithm and an online adaptive fast parameters calculation method. Finally, OAFC is applied to a large inertia system — wet raw material mill in a cement plant. The practical application and the control results demonstrate the effectiveness and implementability of the proposed approach.

Research on Lyapunov Exponent of Chaos Feature in Different Stress Stage of Concrete Joint System

2010 ◽  
Vol 143-144 ◽  
pp. 120-124 ◽  
Author(s):  
Jun Wei Song
Keyword(s):  
Compressive Strength ◽  
Steady State ◽  
Stability Criterion ◽  
System Stability ◽  
Stress System ◽  
Chaotic State ◽  
Whole Process ◽  
Strain Stress ◽  
The Stability ◽  
Relationship Of

: According to the research on whole curves of strain-stress of concrete materials, the paper illustrates in evidence features of stages and shows that the discrete feature of curve often occurs in strain-softening stage. After chaotic dynamic analysis of testing datas, it presents that system of whole process of strain-stress evolves from ordered steady state to low chaotic state and then to high chaotic state along with increase of compressive strength. The linear relationship of strain- stress grows evident and the system evolves from strong ordered steady state to low chaos state. The strain-stress system before compressive strength peak is basically in weak chaotic state. The is proposed to be the stability criterion of concrete features in different stress stages, and the is regarded as the representative value of the system stability degree. The calculation of example shows that the stability criterion definited by the proposed method is consistent with the actural situation.

scholarly journals Importance of various antioxidant enzymes for cell stability. Confrontation between theoretical and experimental data

1992 ◽  
Vol 286 (1) ◽  
pp. 41-46 ◽  
Author(s):  
J Remacle ◽  
D Lambert ◽  
M Raes ◽  
E Pigeolet ◽  
C Michiels ◽  
...  
Keyword(s):  
Experimental Data ◽  
Antioxidant Enzymes ◽  
Steady State ◽  
Qualitative Description ◽  
Rate Equations ◽  
Stable Steady State ◽  
General View ◽  
Complex Situation ◽  
Cell Stability ◽  
The Stability

A theoretical model was developed taking into account the production and destruction of oxygen-derived free radicals. The steady state of the system was derived by using the rate equations of these reactions, and the stability of the system was tested. In the simplified model, only one stable steady state was found. However, we know that glutathione peroxidase can be inhibited by hydroperoxides, and, when incorporated into the model, this effect led to a complex situation with the presence of some stable and some unstable domains according to the concentration of either the enzyme or the hydroperoxide. This qualitative description of the system was compared with experimental data on the protection given by three antioxidant enzymes, and concordance of data was found which allows some quantification of the system. A general view of the efficiency of the three antioxidant enzymes and of the stability of the system according to their concentrations could be produced.

scholarly journals Travelling Wave and Turing Patterns in Subdiffusive Autocatalytic Systems

2021 ◽  
Author(s):  
Uttam Kumar ◽  
Pushpavanam Subramanian
Keyword(s):  
Steady State ◽  
Stability Boundary ◽  
Mean Square Displacement ◽  
Travelling Wave ◽  
Turing Patterns ◽  
Logistic Growth ◽  
Stable Steady State ◽  
Phase Plane Analysis ◽  
Plane Analysis ◽  
The Stability

Abstract In this work, we analyse autocatalytic reactions in complex and disordered media which are governed by subdiffusion. The mean square displacement of molecules here scale as tγ where 0<γ<1. These systems are governed by fractional partial differential equations. Two systems are analysed i) in the first a logistic growth expression is used to represent the growth kinetics of bacteria. Here the system dynamics is governed by a single variable. ii) the second system is a two variable cubic autocatalytic system in a porous media. Here each reactant is involved in the autocatalytic generation of the other. These systems have multiple steady states. They exhibit traveling waves moving from an unstable steady state to a stable steady state. The minimum wave velocity has been obtained from phase plane analysis analytically for the first system. In addition, the two variable system also shows Turing patterns in selected regions of parameter space. The stability boundary for Turing patterns for subdiffusive system is found to be the same as that for regular diffusive systems obtained by Seshai et al. [1]. System behaviour as predicted by the stability analysis is verified using a robust implicit numerical method based on L1 scheme.

scholarly journals EIGENVALUE METHOD AND LINEARIZATION FOR THE STEADY STATE STABILITY ANALYSIS OF JAMSHORO THERMAL POWER PLANT (JTPP)

2020 ◽  
Vol 15 (12) ◽  
Author(s):  
Zulfiqar Ali Shahani
Keyword(s):  
Steady State ◽  
Power Plant ◽  
Power System ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
Electrical Power ◽  
System Stability ◽  
Eigenvalue Method ◽  
The Stability ◽  
Steady State Stability

Electrical power system without interruption is the need of every consumer. Therefore, supplying electrical power which must be efficient, reliable and secure from any disturbance is the priority of power supply companies. But, due to changes in weather conditions and continuous load variations, small disturbances arise which may lead to severe disturbance. All electrical generating stations are interconnected, so a failure in any one unit can affect other generating units, therefore analysis is compulsory to solve the problem in the least time, and avoid a further big loss. Analysis of steady-state stability or transient stability plays a key role in a power system which helps to understand the behavior of a dynamic system. The stability problem is concerned with the behavior of the generating station when the system puts on either small or large disturbance. In this work, the steady-state stability (SSS) analysis of the Jamshoro thermal power plant (JTPP) is analyzed by using the eigenvalue method and linearization technique at four different reheat gain values. We develop a nonlinear mathematical model of JTPP and discuss its linearized form, and examine the behavior of the system stability using eigenvalues. The eigenvalue method analyzes the behavior of synchronous machine when system load varies continually. Numerical values of eigenvalues consist of either real part or real as well as imaginary parts. These eigenvalues help to understand the stability of the system, as to whether the system is stable or not.

Sign in / Sign up

Export Citation Format

Share Document