Sharif Digital Repository

This paper has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions, we have employed Takens embedding theorem which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named "Takens transformation." Takens transformation just needs time series of one of the measurable states. This transformation... 

Despite that the border between chaotic and stochastic systems is exactly defined, scientists, use high dimensional chaotic dynamics to model numerous stochastic models and sometimes use stochastic models to study chaotic systems. In this paper, we have investigated chaotic systems with a stochastic approach and proposed an estimator for the chaotic system which is used to present different algorithms for chaos control, extreme event prediction and extreme event mitigation. The stochastic estimator is constructed by meshing the phase space and applying the cell mapping method (with some considerations) which provides us with a model-free approximation of the systems. The algorithms are ideal... 

This paper has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions, we have employed Takens embedding theorem which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named "Takens transformation." Takens transformation just needs time series of one of the measurable states. This transformation... 

The development of graphene-based nanocomposites is currently the issue of enormous research interest. Recent advancements have exhibited that semiconductor/graphene nanocomposites can be purposed as a promising new category of catalysts for the heterogeneous photocatalytic treatment of wastewaters. Since semiconductor/graphene nanocomposites have been found efficient in degradation of organic pollutants, photodegradation of phenol and phenolic compounds as hazardous contaminants in aqueous solution has been most widely investigated by these aforementioned nanocomposites. In the present review, after introduction on the properties and the different synthesis methods of semiconductor/graphene... 

This study devoted to developing an efficient adsorbent with the excellent adsorption performance of heavy metals and bacteria capturing. Polyresorcinol@CoFe2O4 was synthesized by one-step hydrothermal reaction followed with doping MnS nanoparticles. The composite was characterized with SEM,TEM, BET, EDX, XRD, zeta potential measurement and Raman spectroscopy. Optimization of effective parameters on heavy metal adsorption, i.e., pH, contact time and adsorbent dosage, was performed with response surface methodology using Box–Behnken design. The sorbent showed good performance for Pb(II), Ag(I) and Cr(VI) removal with convenient magnetic separation operation with an adsorption capacity of... 

In this paper, a new approach to control continuous time chaotic systems with an unknown governing equation and limitation on the measurement of states, has been investigated. In many chaotic systems, disability to measure all of the states is a usual limitation, like in some economical, biological and many other engineering systems. Takens showed that a chaotic attractor has an astonishing feature in which it can embed to a mathematically similar attractor by using time series of one of the states. The new embedded attractor saves much information from the original attractor. This phenomenon has been deployed to present a new way to control continuous time chaotic systems, when only one of... 

In this research, an efficient biosorption system was developed for methylene blue adsorption over in situ hydrothermally synthesized magnetite 4-hydroxybenzoic acid cellulose nanohybrid. The material was characterized with EDX, VSM, FT-IR, FESEM, and TEM techniques. Results showed that the nanohybrid is a micro-cluster composed of stacked nanoscale particles. Multivariate optimization with Box–Behnken design was used to evaluate effective parameters on adsorption and their interaction. Results showed that pH, shacking time, and adsorbent dosage are effective parameters on MB adsorption. Adsorption rate is fast with equilibrium time of 5.5 min. Isotherm study revealed that the adsorption... 

In this research, an efficient biosorption system was developed for methylene blue adsorption over in situ hydrothermally synthesized magnetite 4-hydroxybenzoic acid cellulose nanohybrid. The material was characterized with EDX, VSM, FT-IR, FESEM, and TEM techniques. Results showed that the nanohybrid is a micro-cluster composed of stacked nanoscale particles. Multivariate optimization with Box–Behnken design was used to evaluate effective parameters on adsorption and their interaction. Results showed that pH, shacking time, and adsorbent dosage are effective parameters on MB adsorption. Adsorption rate is fast with equilibrium time of 5.5 min. Isotherm study revealed that the adsorption... 

An efficient dye decolorization platform was developed through one-step hydrothermally route based on magnetic polymeric resin and employed in aqueous crystal violet (CV) adsorption. The polymer nanohybrid composed of ZnFe2O4 and hydroxybenzoic acid–resorcinol resin as metal and organic fragment, respectively. Several techniques such as X-ray diffraction, N2 – adsorption desorption, vibration sample magnetometer, field emission scanning electron microscopy and Fourier transform infrared spectroscopy were employed for characterization of as-prepared nanohybrid. CV adsorption showed low equilibrium time within 10 min with the adsorption capacity of 83.3 mg g–1. Regeneration of the sorbent... 

An efficient organic/inorganic magnetic nanohybrid of MgAl@CuFe2O4-polylysine was successfully synthesized and employed as a suitable adsorbent for removal Cr(VI) and methyl orange from water solution. The prepared nanohybrid was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and thermogravimetric analysis. The nanohybrid of MgAl@CuFe2O4-polylysine was employed to adsorb anionic species, i.e., Cr(VI) and methyl orange through electrostatic attraction, ligand exchange and ion exchange. Multivariate optimization with Box-Behnken design was used to evaluate effective parameters such as dosage of adsorbent,... 

This study focuses on developing an efficient material that integrates high adsorption performances of dye and antibiotics as well as effective oxidation activity of it. Herein, we report a facile method to synthesize polyresorcinol@CoFe2 O4 via a one-step hydrothermally route. The prepared composite possesses multifunctional performance for methylene blue (MB) and tetracycline (TC) removal with appropriate magnetic separation operation and significant removal ability with an adsorption capacity of 51.48 and 28.16 mg g–1, respectively. Meanwhile, the aforementioned composite exhibits a high oxidation activity toward MB and TC molecules where the adsorption capacity increases to 1,723 and 120... 

This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson's ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The... 

An economical epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite, CH-EP@Fe3O4/AC, was successfully synthesized and used as a suitable adsorbent material for removal of a triphenylmethane cationic dye, Malachite green (MG), an anionic dye, Reactive red 120 (RR120), and Mercury ions (Hg2+) from aqueous solution. The prepared adsorbent has been characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller analysis as well as Vibrating sample magnetometer. According to the result of Brunauer–Emmett–Teller isotherm, the prepared adsorbent has a specific surface area...