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A unique metamaterial inspired star-slot UWB antenna with soft surface ground
No full textA metamaterial (MTM) inspired star-slot planar microstrip line fed ultra-wideband (UWB) antenna having a soft-surface ground structure is presented in this paper. The proposed antenna comprises periodically repeated star-slot unit cells on patch (radiating) side. This feature helps achieve an UWB from 4.0 to 16.2 GHz. Back lobe radiation is suppressed when the ground metallic part is partially replaced by periodic square-shaped cross-slot soft-surface unit cells. The dispersion relation exhibits a wide bandgap in the resonance frequency regions. The backward wave displays a balanced condition when series and shunt frequencies are equivalent (ωse = ωsh), whereas it displays an unbalanced condition when they are not (ωse ≠ ωsh). The periodic star rings etched on the metal patch enhance bore sight gain to a maximum of 8 dBi at 9.2 GHz. The antenna is fabricated on a Duroid substrate with overall dimensions of 27.00 × 31.40 × 1.57 mm3 with a 10.0 GHz of the resonant frequency. The numerical and experimental results verify the proposed artificial metamaterial design structure that matches the theory. © 2020, © 2020 Taylor & Francis
Improved Salp Swarm Algorithm based on opposition based learning and novel local search algorithm for feature selection
No full textMany fields such as data science, data mining suffered from the rapid growth of data volume and high data dimensionality. The main problems which are faced by these fields include the high computational cost, memory cost, and low accuracy performance. These problems will occur because these fields are mainly used machine learning classifiers. However, machine learning accuracy is affected by the noisy and irrelevant features. In addition, the computational and memory cost of the machine learning is mainly affected by the size of the used datasets. Thus, to solve these problems, feature selection can be used to select optimal subset of features and reduce the data dimensionality. Feature selection represents an important preprocessing step in many intelligent and expert systems such as intrusion detection, disease prediction, and sentiment analysis. An improved version of Salp Swarm Algorithm (ISSA) is proposed in this study to solve feature selection problems and select the optimal subset of features in wrapper-mode. Two main improvements were included into the original SSA algorithm to alleviate its drawbacks and adapt it for feature selection problems. The first improvement includes the use of Opposition Based Learning (OBL) at initialization phase of SSA to improve its population diversity in the search space. The second improvement includes the development and use of new Local Search Algorithm with SSA to improve its exploitation. To confirm and validate the performance of the proposed improved SSA (ISSA), ISSA was applied on 18 datasets from UCI repository. In addition, ISSA was compared with four well-known optimization algorithms such as Genetic Algorithm, Particle Swarm Optimization, Grasshopper Optimization Algorithm, and Ant Lion Optimizer. In these experiments four different assessment criteria were used. The rdemonstrate that ISSA outperforms all baseline algorithms in terms of fitness values, accuracy, convergence curves, and feature reduction in most of the used datasets. The wrapper feature selection mode can be used in different application areas of expert and intelligent systems and this is confirmed from the obtained results over different types of datasets. © 2019 Elsevier Lt
First-principles computations of YxGa1−x As-ternary alloys: a study on structural, electronic, optical and elastic properties
No full textIn this work, the first-principles computational study on the structural, elastic, electronic and optical properties of Y xGa 1 - xAs as a function of yttrium concentration (x) is presented. The computations are performed using the full-potential linearized augmented plane wave plus local orbital method designed within density functional theory. Firstly, we performed our calculations on the most stable phases, NaCl and zinc blende, then their transition pressure for each concentration is determined and analysed. Our computed results for the zero yttrium concentration are found consistent with the available experimental measurements as well as with theoretical predictions. Moreover, the dependencies of these parameters upon yttrium concentration (x) were found to be non-linear. We also report computed results on electronic-band structure, electronic energy band gap results and density of states. A systematic study on optical properties to analyse its optoelectronic character and elastic properties is presented. © 2019, Indian Academy of Sciences
Synthesis, characterization and crystal structure of new tetrahydro-β-carboline as acetylcholinesterase inhibitor
No full textIn this study, a new tetrahydro-β-carboline derivative, 2-benzoyl-6-methoxy-9-methyl-1-phenyl-1,2,3,4-tetrahydro-β-carboline has been synthesized through a three-steps reaction in good yield (76%). The structure of this compound was characterized by different spectroscopic methods including NMR (1D and 2D), UV, IR and MS. Molecular structure of the synthesized compound was also confirmed by single crystal X-ray diffraction technique. Further, evaluation of in vitro acetylcholinesterase (AChE) inhibitory activity showcased the potential of this compound as AChE inhibitor with an IC50 value of 26.52 ± 0.79 μM. In addition, this compound showed minimal toxicological profile at cellular level. Docking simulation illustrated a highly selective binding at peripheral side of AChE via hydrophobic interactions. In silico prediction of blood-brain barrier (BBB) permeation and ADMET properties of the compound was also reported. © 2019 Elsevier B.V
Development of leak-free phase change material aggregates
No full textThis study aims to develop leak-free phase change material (PCM)-aggregates through a two-step pelletization process. Microencapsulated PCM (mPCM) was incorporated into the core of the aggregate during the granulation process and then coated with a PCM-free shell to overcome the PCM leakage. The thermal properties of pellets cured under CO2 and natural air, including their enthalpy and thermal conductivity as well as their thermal stability were measured and compared using differential scanning calorimeter, thermogravimetric analyses and transient plane source method. The effect of both mPCM content and CO2 curing on the strength of the aggregates was also analyzed. The results revealed that mPCM can be used to produce lightweight aggregates with a distinct core-shell structure having an oven-dry bulk density, water absorption and latent heat of about 788 kg/m3, 14% and 18 kJ/kg, respectively. In addition, the shell layer can effectively prevent the leakage of the PCM and can be further densified by CO2 curing. In addition, CO2 curing contributed to the improvement of the overall physical properties and early strength development of the aggregates. The developed leak-free PCM-aggregates would then allow adding PCM into the concrete mix as an inert material and hence suppress the degradation of mechanical strength and high-water demand caused by the direct use of mPCM in concrete. © 2019 Elsevier Lt
A Critical Outlook on the Role of Research Practices in Laboratory towards Student Skills Development in Malaysian and Japanese Public Universities
Get PDFDeveloping talented graduates to fulfil market challenges is a formidable task for higher education today. By using qualitative method, Malaysian and Japanese professors in selected public universities were interviewed in order to investigate how research practices in laboratory contribute towards student skills development. The result shows that laboratory practices such as group work, mentoring and closed monitoring in organization enhance student employability skills. It is suggested that chain mentoring system from professors to junior researchers to be practiced as a succession planning in developing potential leaders. Closed monitoring between principal investigator, senior and junior researchers is also significant to support not only for professional skills, but also for personality growth and emotional support
Q‐switching pulses generation with samarium oxide film saturable absorber
No full textQ-switching pulses generation in an erbium-doped fiber laser (EDFL) was demonstrated by using a samarium oxide (Sm2O3) film as a saturable absorber (SA) for the first time. The passively Q-switched EDFL operated stably at 1567 nm with tunable repetition rates, ranging from 47 to 66 kHz with the increase in pump power from 51.0 to 88.1 mW. At 88.1 mW pump power, the maximum pulse energy and the minimum pulse width were obtained at 26 nJ and 5.6 μs, respectively. These results demonstrated that the proposed Sm2O3 SA is viable for the construction of a flexible and reliably stable Q-switched pulsed fiber laser in the 1.5 μm region. © 2019 Wiley Periodicals, Inc
Nonlinear studies of graphene oxide and its application to moisture detection in transformer oil using D-shaped optical fibre
No full textThis paper reports nonlinear optical response studies of thin layers using graphene oxide (GO) and their performance for detecting water content in transformer oil using three sets of approaches. The sensor performance is evaluated based on bare optical fibre, D-shape optical fibre integrated with GO and the effects of the covering device with polydimethylsiloxane (PDMS). The improvement of this study is to ensure the stability of the recorded signal. The nonlinear optical response of the prepared dispersion was explored using the Z-scan technique with an 800 nm continuous wave laser beam. Taking advantage of the graphene-induced evanescent field using D-shape optical fibre with PDMS covers on the device can give high sensitivity and good stability for water dissolved in the oil at 1550 nm. We measured fluctuations in transmitted light associated with varying water contents ranging from 16 to 38 ppm. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group
Thermal characterization of phase difference among the LP modes in two-mode fibers based on numerical approach
No full textIn this work, we present the use of stochastic parallel gradient descent (SPGD) method for determination of thermal characteristic of the phases of LP11o and LP11e modes in relative to LP01 mode in two-mode fibers. Based on the output beam of the fiber, the composition of mode intensity and the respective phase are numerically determined. The findings indicate that modal phases of LP11o and LP11e linearly vary with increasing temperature. Their thermal sensitivities of LP11o and LP11e modes in relative with LP01 mode are determined. © 2020 Elsevier Gmb
Thermoluminescence features of commercial glass and retrospective accident dosimetry
No full textFive window glass brands popularly used in Bangladeshi dwellings have been analyzed for retrospective accident dosimetry, being inexpensive, highly effective as a barrier to moisture and naturally transparent at optical wavelengths. In examining their potential for dosimetry, study has been made of the annealing – irradiation - readout steps contributing to characterization of the various key thermoluminescence properties. These include the respective glow curves, relative sensitivity, dose response, energy response, reproducibility and fading. An ERESCO model 200 MF4-RW X-ray machine and a Gammacell-220 60Co source was used for sample irradiation, while a Harshaw 3500 TLD reader (USA) supported by WinREMS software was used for TL readouts. Within the γ-radiation dose range up to 50 Gy, the various TL parameters show Nasir glass (a locally produced glass brand) to offer the most promising performance for retrospective dosimetry. Fading studies indicate the reconstruction of absorbed dose to be possible for periods of up to four weeks post-exposure. Energy dispersive X-ray analysis shows the Zeff of the various glass to be in the range 12.5–15.1, closely according with that of TLD-200, a commercial dosimeter used for low-level environmental radiation dosimetry. Present work constitutes the first such study of low-cost commercial glass for doses in the range 10–50 Gy, previous literature relating to doses from 50 Gy up to 20 kGy. © 2019 Elsevier Lt