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Mohammad Tariqul Islam,심재진,유바라즈할도라이,웬방호아,Muhammad Naoshad Islam,나춘섭 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.6
Poly(vinyl acetate) (PVAc) was synthesized by the atom transfer radical polymerization of vinyl acetate(VAc) in supercritical carbon dioxide using CuBr/2,2':6',2''-terpyridine complex as a catalyst and ethyl 2-bromoisobutyrateas an initiator. Polymerization proceeded in a controlled manner, and low to moderate conversion wasachieved within a reasonable time. The effects of the monomer amount, temperature, pressure, initiator, and ligandloading on monomer conversion, molecular weight and molecular weight distribution of the polymer were examined. The reaction kinetics was also investigated. The polymerization reaction was found to be first-order with respect to themonomer concentration. The molecular weights of the resulting PVAc increased linearly with increasing VAc conversion.
Design and analysis of a new composite double negative metamaterial for multi-band communication
Mohammad Jakir Hossain,Mohammad Rashed Iqbal Faruque,Mohammad Tariqul Islam 한국물리학회 2017 Current Applied Physics Vol.17 No.7
In this paper, a double C-shaped structure of double negative composite metamaterial is designed and depicts in configurations that can capable in a multi-band microwave frequency band. The design has achieved relative negative permeability, relative negative permittivity and relative negative refractive index. Analysis and comparison were done by using four configurations of composite metamaterial such as horizontal 1 1 array and vertical 1 1 array structures and the horizontal 1 1 and vertical 1 1 unit-cell configurations. Multi-band operating frequencies namely, S-band, C-band and X-band have been achieved using all configurations. The proposed metamaterial size is 1.2 cm 1.2 cm 0.16 cm which includes all geometrical parameters to fit the design inside the substrate area. Computer Simulation Technology (CST) is adopted to investigate this design where an incident electromagnetic wave travelling along the positive z-axis with an E-field polarized along the y-axis. The results of the proposed metamaterial depict multi-band metamaterial response over the frequency span from 1 to 15 GHz. The effective medium ratio of the metamaterial unit-cell is 7.44. Moreover, the results clearly seen that the single-negative and double-negative metamaterial characteristics of the unit-cell and arrays over the multi-band. The dimensions and scattering parameters of the proposed double C-shaped metamaterial are suitable for the S -band, C-band and X-band applications.
Self-assembly of a liquid crystal ABA triblock copolymer in a nematic liquid crystal solvent
Islam, Mohammad Tariqul,Kamal, Tahseen,Shin, Taegyu,Seong, Baekseok,Park, Soo-Young Elsevier 2014 Polymer Vol.55 No.16
<P><B>Abstract</B></P> <P>An ABA type triblock copolymer, consisting of liquid crystalline polymer (LCP, poly(4-cyanobiphenyl-4-oxyundecylacrylate)) ‘A’ end blocks and a deuterated polystyrene (dPS) ‘B’ mid block (LCP–dPS–LCP) was successfully synthesized by atom transfer radical polymerization (ATRP). The number average molecular weight (<I>M</I> <SUB>n</SUB>) of LCP–dPS–LCP was LCP (7.1 K)–dPS (19.4 K)–LCP (7.1 K) with a polydispersity index (PDI) of 1.41. LCP–dPS–LCP was self-assembled in a nematic liquid crystal solvent of 4-pentyl-4′-cyanobiphenyl (5CB) into spherical micelles with a LCP corona and a dPS core, in which dPS was folded to produce a V-shape structure. Micellar structures of LCP–dPS–LCP in 5CB were examined by small angle neutron scattering at various block copolymer concentrations and temperatures using a curve fitting method. The critical micelle concentration was 0.25 wt% and the self-assembled micelles dissociated into unimers at 33 °C, which is lower than the nematic to isotropic transition temperature (<I>T</I> <SUB>ni</SUB>) of 5CB (36 °C). The entropic penalty imposed on dPS by the ordered nematic state of the 5CB solvent caused phase separation of the flexible dPS block to form micelles, which vanished above the <I>T</I> <SUB>ni</SUB> of the 5CB solvent. Magnetic field-induced global orientation of 5CB revealed the structure of the dPS core of the micelle to be prolate (an elongated sphere) oriented with its long axis along the direction of the applied magnetic field.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hasan Mohammad Kamrul,Islam Md. Tariqul,Akter Rojina,Roshni Nasima Akther 한국생태학회 2022 Journal of Ecology and Environment Vol.46 No.3
Background: Increasing land demands for food production have led to biodiversity loss and land degradation in the Madhupur Sal forest. Reforestation activities such as agroforestry and woodlot plantation support the conservation of diversity, restoration of forest and prevention of soil erosion in degraded natural Sal forest. Knowing about these reforestation activities, this study is needed to compare the species composition, richness, and soil nutrients of these two plantation activities to the natural Sal forest in the degraded Madhupur Sal forest in Bangladesh. Results: The analysis showed that in between the reforestation activities, the highest Shannon- Wiener index (1.79), evenness (0.60) and Simpson’s index (0.79) were found in the agroforestry site compared to the woodlot plantation site. On the contrary, the highest species richness (n = 14), tree basal area (19.56 m2 ha−1), Margalef’s index (1.96) were recorded in woodlot plantation than in the agroforestry site. We observed that at 0–15 cm depth, soil organic matter (2.39%), total nitrogen (0.14%), available phosphorous (62.67 μg g−1) and exchangeable potassium (0.36 meq/100 g) in agroforestry plots were significantly higher compared to other forest sites. At topsoil (15–30 cm depth), soil organic matter (1.67%) and available phosphorous (21.09 μg g−1) were found to be higher in agroforestry site. Conclusions: Both reforestation approaches improved soil function, although woodlot plantation had the higher species richness. Therefore, plantation activities by the sustainable implementation of these two practices are the best alternative to restore the biodiversity, richness and conserve soil fertility in the Madhupur Sal forest of Bangladesh.
Adaptive Beamforming Algorithms for Smart Antenna Systems
Shahera HOSSAIN,Mohammad Tariqul ISLAM,Seiichi SERIKAWA 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
Wireless communication is one of the most rapidly growing industries. The high demand for wireless communication services had led to an increase in system capacity. Then most elementary solution would be to increase bandwidth; however, this becomes ever more challenging as the electromagnetic spectrum is becoming increasingly congested. The ever-increasing demand for increased capacity in wireless communications services has led to developments of new technologies that exploit space selectivity. This is done through smart-antenna arrays and the associated adaptive beamforming algorithms. Smart-antenna systems provide opportunities for higher system capacity and improved quality of service among other things In this paper, two non-blind algorithms: Least Mean Square (LMS) and Normalized Least Mean Square (NLMS) algorithms were compared for a robust smart antenna system. It has been found that NLMS performs better in many respects than LMS and so we propose NLMS to be used by mobile companies when they will use smart antenna. Our findings are explained in details in the result and analysis section with graphs. Our comparison and findings were simulated using MATLAB.