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CONTENTS
Volume 9, Number 4, December 2020
 


Abstract
α-mangostin imprinted polymers have been synthesized by a non-covalent imprinting approach with α-mangostin as a template molecule. The α-mangostin molecularly imprinted polymers (MIPs) prepared by radical polymerization using methacrylic acid, ethlylene glycol dimethacrylate, benzoyl peroxide, and acetonitrile, as a monomer, crosslinker, initiator, and porogen, respectively. The template was removed by using methanol:acetic acid 90:10 (v/v). The physical characteristics of the polymers were investigated by Fourier Transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The rebinding studies were carried out by batch methods. The results exhibited that the MIPs was able to adsorb the α-mangostin at pH 2 and the contact time of 180 min. The kinetic adsorption data of α-mangostin performed the pseudo-second order model and followed the Langmuir isotherm model with the adsorption capacity of 16.19 mg.g-1. MIPs applied as a sorbent material in solid-phase extraction, namely molecularly imprinted solid-phase extraction (MISPE) and it shows the ability for enrichment and clean-up of α-mangostin from the complex matrix in medicinal herbal product and crude extract of mangosteen (Garcinia mangostana L.) pericarp. Both samples, respectively, which were spiked with α-mangostin gives recovery more than 90% after through by MISPE in all concentration ranges.

Key Words


Address
(1) Neena Zakia, Muhammad A. Zulfikar, Muhammad B. Amran:
Analytical Chemistry Research Group, Institut Teknologi Bandung, Jalan Ganesha No 10, Bandung, 40132, Indonesia;
(2) Neena Zakia:
Department of Chemistry, Universitas Negeri Malang, Jalan Semarang No 5, Malang, 65145, Indonesia.

Abstract
A theoretical method to predict the interfacial stresses in the adhesive layer of reinforced concrete beams strengthened with porous FRP plate is presented in this paper. The effect due to porosity is incorporated utilizing a new modified rule of mixture covering the porosity phases. The adherend shear deformations have been included in the present theoretical analyses by assuming a linear shear stress through the thickness of the adherends. Remarkable effect of the porosity has been noted in the results. Indeed, the resulting interfacial stresses concentrations are considerably smaller than those obtained by other models which neglect the porosity effect. It was found that the interfacial stresses are highly concentrated at the end of the FRP plate, the minimization of the latter can be achieved by using porous FRP plate in particular at the end. It is also shown that the interfacial stresses of the RC beam increase with volume fraction of fibers, but decrease with the thickness of the adhesive layer.

Key Words
interfacial stresses; reinforced concrete beam; porous FRP plate

Address
(1) Laboratory of Geomatics and sustainable development, University of Tiaret, Algeria;
(2) Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria.

Abstract
The aim of the present investigation is to examine the propagation of plane harmonic waves in transversely isotropic homogeneous magneto visco thermoelastic rotating medium with fractional order heat transfer and two temperature. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal) in frequency domain. phase velocities, specific loss, penetration depth, attenuation coefficients of various reflected waves are computed and depicted graphically. The effects of viscosity and fractional order parameter by varying different values are represented graphically.

Key Words
thermoelastic; transversely isotropic; magneto-visco thermoelastic rotating medium; fractional-order heat transfer; plane harmonic wave propagation

Address
(1) Iqbal Kaur:
Government College for Girls, Palwal, Kurukshetra, Haryana, India;
(2) Parveen Lata:
Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India;
(3) Kulvinder Singh:
Kurukshetra University Kurukshetra, Haryana, India.

Abstract
In this study, Mangifera Indica tree sawdust reinforced bisphenol-A aniline based benzoxazine composites were prepared by varying the sawdust from 20 wt% to 45 wt%. Thermogravimetric analysis of composites revealed excellent compatibility between polybenzoxazine and sawdust from the remarkable growth in char yield from 22% (neat resin) to 36% (for highly filled) and glass transition temperature from 151 to 165°C. Ultimate weight loss of the composites evaluated from the Derivatives of TG plots. Limiting oxygen index values of the composites reported considerable growth i.e., from 28 to 32 along with the increase in filler content. Differential scanning calorimetry results showed that sawdust particles have an insignificant effect on curing temperature (219°C) for the raise in sawdust content. Structure of the sawdust, benzoxazine monomer, polybenzoxazine and composites were studied using Fourier transformation infrared spectroscopy. Overall, polybenzoxazine composites with sawdust as filler showed improved thermal properties when compared with pure polybenzoxazine.

Key Words
composite material; thermal properties; structural properties; sawdust; polybenzoxazine

Address
Department of Mechanical Engineering, Vignan's Foundation for Science Technology and Research, Guntur, Andhra Pradesh-522213, India.


Abstract
This article reviews findings and progresses in the past decade on manganese-aluminium (MnAl) based magnets as the interest has been revived to fulfill their potential as commercial magnets. The challenges in developments of these rare-earth-free magnets are to acquire a high remanence and coercivity from the ferromagnetic τ-phase in MnAl alloys. To this end, the phase transformation to this τ-MnAl with L10 body centered tetragonal structure has been promoted by a variety of methods and a few percents of carbon (C) is often added to prevent the phase decomposition. Magnetization and coercivity are not only influenced by the phase composition but also the microstructure. The fabrication processes and factors affecting the phase and microstructure are therefore covered. Finally, the productions of bulk MnAl magnets are addressed.

Key Words
rare-earth-free magnet; manganese-aluminium; ferromagnetic phase; coercivity; magnetization

Address
(1) Division of Physics, School of Science, Walailak University, 222 Thaiburi, Thasala, Nakhon Si Thammarat, 80160, Thailand;
(2) Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, 328 Si Ayutthaya Road, Bangkok 10400, Thailand;
(3) Functional Materials and Nanotechnology Center of Excellence, Walailak University, 222 Thaiburi, Thasala, Nakhon Si Thammarat, 80160, Thailand.


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