Abstract: In this study, recursive and adaptive backstepping nonlinear controllers are proposed t... more Abstract: In this study, recursive and adaptive backstepping nonlinear controllers are proposed to, respectively, control and synchronize the biological system. The designed recursive nonlinear backstepping controller is capable of stabilizing the biological system ...
Numerical simulations have been used to investigate the synchronization behavior of a unidirectio... more Numerical simulations have been used to investigate the synchronization behavior of a unidirectionally coupled pair of double-well duffing oscillators (DDOs). The DDOs were simulated in their structurally stable chaotic zone and their state variables were found to completely synchronized. The essential feature of the transition to the synchronous state is shown to correspond to a boundary crisis in which the cross-well chaotic attractor is destroyed.
ABSTRACT The synchronization dynamics of two linearly coupled pendula is studied in this paper. B... more ABSTRACT The synchronization dynamics of two linearly coupled pendula is studied in this paper. Based on the Lyapunov stability theory and Linear matrix inequality (LMI); some necessary and sufficient conditions for global asymptotic synchronization are derived from which an estimated threshold coupling kth, for the on-set of full synchronization is obtained. The numerical value of kth determined from the average energies of the systems is in good agreement with theoretical analysis. Prior to the on-set of synchronization, the boundary crisis of the chaotic attractor is identified. In the bistable states, where two asymmetric periodic attractors co-exist, it is shown that the coupled pendula can attain multistable states via a new dynamical transition—the basin crisis that occur prior to the on-set of stable synchronization. The essential feature of basin crisis is that the two co-existing attractors are destroyed while new three or more co-existing attractors of the same or different periodicity are created. In addition, the linear perturbation technique and the Routh–Hurwitz criteria are employed to investigate the stability of steady states, and clearly identify the different types of bifurcations likely to be encountered. Finally, two-parameter phase plots, show various regions of chaos, hyperchaos and periodicity.
Effects of red and blue colour of monochromatic lights at intensities of 500 lux, 1000 lux, 1500 ... more Effects of red and blue colour of monochromatic lights at intensities of 500 lux, 1000 lux, 1500 lux and 2000 lux on the growth of <em>Oedogonium</em> sp. The cell growth was monitored by measuring the optical density (absorbance) at 680 nm using a Digital Spectrophotometer. GC-MS analysis was also carried out for extraction of <em>Oedogonium </em>sp<em>.</em> The results showed maximum values for absorbance 0.378 Au and 0.364 Au for blue and red light respectively at 2000 lux. While minimum values of 0.237 Au and 0.249 Au were obtained at intensity of 500 lux for blue light and red light respectively. The pigment concentration showed a consistent daily increase, with a maximum pigment concentration of chlorophyll a 4.31 mg/L and chlorophyll b 7.36 mg/L for blue light and chlorophyll a 4.15 mg/L and chlorophyll b 7.09 mg/L for red light at 2000 lux. Result for GC-MS analysis produced 12 volatile components; 10 hydrocarbons and 2 acids, which impli...
This paper investigates the synchronization and anti-synchronization behaviour of two identical d... more This paper investigates the synchronization and anti-synchronization behaviour of two identical double-hump Duffing-Van der Pol oscillator (DHDVP) evolving from different initial conditions using the active control technique based on the Lyapunov stability theory (LST) and the Routh-Hurwitz criteria (RHC). The designed controllers, with three different choices of the coefficient matrix of the error dynamics that satisfy the LST and RHC, are found to be effective in the stabilization of the error states at the origin, thereby, achieving synchronization and anti-synchronization between the states variables of two DHDVP oscillators. Interestingly, one of the choices leads to a single control function, thereby, reducing controller complexity for easy implementation. The results are validated by numerical simulations.
The synthesis, characterization and swelling equilibrium of chitosan film in water-solvent mixtur... more The synthesis, characterization and swelling equilibrium of chitosan film in water-solvent mixtures were investigated. Chitosan film was prepared by reacting chitosan with 2% v/v glacial acetic acid. The film was characterized by Fourier transform Infra-red spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) to determine its structure and morphology. The swelling behavior of this chitosan film was further investigated in water-solvent (methanol, ethanol, butanol and acetone) mixtures gravimetrically at different temperatures and pH. The equilibrium and dynamic swelling properties were studied to investigate the pH-sensitive behavior of the gels. The hydrogel demonstrated critical swelling behavior as the pH approached 6.8. The dynamic swelling was performed and the results were analyzed using a second-order model to calculate the time constant of the swelling. The values of percentage equilibrium swelling of chitosan film in water were higher than...
This work examines the effect of block sizes on attributes (robustness, capacity, time of water- ... more This work examines the effect of block sizes on attributes (robustness, capacity, time of water- marking, visibility and distortion ) of watermarked digital images using Discrete Cosine Transform (DCT) function. The DCT function breaks up the image into various frequency bands and allows watermark data to be easily embedded. The advantage of this transformation is the ability to pack input image data into a few coefficients. The block size 8 x 8 is commonly used in watermarking. The work investigates the ef- fect of using block sizes below and above 8 x 8 on the attributes of watermark. The attributes of robustness and capacity increase as the block size increases (62-70db, 31.5-35.9 bit /pixel). The time for watermarking reduces as the block size increases. The watermark is still visible for block sizes below 8 x 8 but invisible for those above it. Distortion decreases sharply from a high value at 2 x 2 block size to minimum at 8 x 8 and gradually increases with block size. The ove...
Abstract: In this study, recursive and adaptive backstepping nonlinear controllers are proposed t... more Abstract: In this study, recursive and adaptive backstepping nonlinear controllers are proposed to, respectively, control and synchronize the biological system. The designed recursive nonlinear backstepping controller is capable of stabilizing the biological system ...
Numerical simulations have been used to investigate the synchronization behavior of a unidirectio... more Numerical simulations have been used to investigate the synchronization behavior of a unidirectionally coupled pair of double-well duffing oscillators (DDOs). The DDOs were simulated in their structurally stable chaotic zone and their state variables were found to completely synchronized. The essential feature of the transition to the synchronous state is shown to correspond to a boundary crisis in which the cross-well chaotic attractor is destroyed.
ABSTRACT The synchronization dynamics of two linearly coupled pendula is studied in this paper. B... more ABSTRACT The synchronization dynamics of two linearly coupled pendula is studied in this paper. Based on the Lyapunov stability theory and Linear matrix inequality (LMI); some necessary and sufficient conditions for global asymptotic synchronization are derived from which an estimated threshold coupling kth, for the on-set of full synchronization is obtained. The numerical value of kth determined from the average energies of the systems is in good agreement with theoretical analysis. Prior to the on-set of synchronization, the boundary crisis of the chaotic attractor is identified. In the bistable states, where two asymmetric periodic attractors co-exist, it is shown that the coupled pendula can attain multistable states via a new dynamical transition—the basin crisis that occur prior to the on-set of stable synchronization. The essential feature of basin crisis is that the two co-existing attractors are destroyed while new three or more co-existing attractors of the same or different periodicity are created. In addition, the linear perturbation technique and the Routh–Hurwitz criteria are employed to investigate the stability of steady states, and clearly identify the different types of bifurcations likely to be encountered. Finally, two-parameter phase plots, show various regions of chaos, hyperchaos and periodicity.
Effects of red and blue colour of monochromatic lights at intensities of 500 lux, 1000 lux, 1500 ... more Effects of red and blue colour of monochromatic lights at intensities of 500 lux, 1000 lux, 1500 lux and 2000 lux on the growth of <em>Oedogonium</em> sp. The cell growth was monitored by measuring the optical density (absorbance) at 680 nm using a Digital Spectrophotometer. GC-MS analysis was also carried out for extraction of <em>Oedogonium </em>sp<em>.</em> The results showed maximum values for absorbance 0.378 Au and 0.364 Au for blue and red light respectively at 2000 lux. While minimum values of 0.237 Au and 0.249 Au were obtained at intensity of 500 lux for blue light and red light respectively. The pigment concentration showed a consistent daily increase, with a maximum pigment concentration of chlorophyll a 4.31 mg/L and chlorophyll b 7.36 mg/L for blue light and chlorophyll a 4.15 mg/L and chlorophyll b 7.09 mg/L for red light at 2000 lux. Result for GC-MS analysis produced 12 volatile components; 10 hydrocarbons and 2 acids, which impli...
This paper investigates the synchronization and anti-synchronization behaviour of two identical d... more This paper investigates the synchronization and anti-synchronization behaviour of two identical double-hump Duffing-Van der Pol oscillator (DHDVP) evolving from different initial conditions using the active control technique based on the Lyapunov stability theory (LST) and the Routh-Hurwitz criteria (RHC). The designed controllers, with three different choices of the coefficient matrix of the error dynamics that satisfy the LST and RHC, are found to be effective in the stabilization of the error states at the origin, thereby, achieving synchronization and anti-synchronization between the states variables of two DHDVP oscillators. Interestingly, one of the choices leads to a single control function, thereby, reducing controller complexity for easy implementation. The results are validated by numerical simulations.
The synthesis, characterization and swelling equilibrium of chitosan film in water-solvent mixtur... more The synthesis, characterization and swelling equilibrium of chitosan film in water-solvent mixtures were investigated. Chitosan film was prepared by reacting chitosan with 2% v/v glacial acetic acid. The film was characterized by Fourier transform Infra-red spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) to determine its structure and morphology. The swelling behavior of this chitosan film was further investigated in water-solvent (methanol, ethanol, butanol and acetone) mixtures gravimetrically at different temperatures and pH. The equilibrium and dynamic swelling properties were studied to investigate the pH-sensitive behavior of the gels. The hydrogel demonstrated critical swelling behavior as the pH approached 6.8. The dynamic swelling was performed and the results were analyzed using a second-order model to calculate the time constant of the swelling. The values of percentage equilibrium swelling of chitosan film in water were higher than...
This work examines the effect of block sizes on attributes (robustness, capacity, time of water- ... more This work examines the effect of block sizes on attributes (robustness, capacity, time of water- marking, visibility and distortion ) of watermarked digital images using Discrete Cosine Transform (DCT) function. The DCT function breaks up the image into various frequency bands and allows watermark data to be easily embedded. The advantage of this transformation is the ability to pack input image data into a few coefficients. The block size 8 x 8 is commonly used in watermarking. The work investigates the ef- fect of using block sizes below and above 8 x 8 on the attributes of watermark. The attributes of robustness and capacity increase as the block size increases (62-70db, 31.5-35.9 bit /pixel). The time for watermarking reduces as the block size increases. The watermark is still visible for block sizes below 8 x 8 but invisible for those above it. Distortion decreases sharply from a high value at 2 x 2 block size to minimum at 8 x 8 and gradually increases with block size. The ove...
Uploads
Papers by Abdulahi Njah