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ON THE POSSIBLE MECHANISMS OF TWO GROUND-LEVEL ENHANCEMENT EVENTS
Firoz, Kazi A.,Moon, Y.-J.,Park, S.-H.,Kudela, K.,Islam, Jamal N.,Dorman, Lev I. IOP Publishing 2011 The Astrophysical journal Vol.743 No.2
<P>We have carried out a case study on the possible mechanism of ground-level enhancement (GLE) occurrence. For this, we have considered two GLE events (GLE69 and GLE70) and scrutinized their relationships with simultaneous soft/hard X-rays as well as solar energetic particle (SEP) fluxes of different energy bands. Although most of the energy bands of the flares maintain strong correlations (r >= 0.8) with the GLEs, depending only on this evidence we could not precisely imply that GLEs can be caused by solar flares. So, we have attempted to understand possible relativistic energies of the GLEs, which have been determined by availing the relativistic traversing time and velocities of the particles along the nominal path of Archimedean spiral magnetic field lines. Results suggest that the energy released from accelerated particles in high-energy (gamma-ray) solar flares might sometimes cause the GLE. We found that during hard X-ray flares <= 7MeV, the relativistic energy (<= 0.23 GeV) of GLE69 was much less than 1 GeV whereas during SEP flares >30 MeV the possible relativistic energy of GLE69 amounts to similar to 2.78 GeV, and this makes us believe that GLE69 might be caused by the energy released from particle accelerations in high-energy solar flares. On the contrary, during hard X-ray (<= 7 MeV) as well as gamma-ray solar flares (>30 MeV) the relativistic energy of GLE70 amounts to <=similar to 0.35 GeV, indicating that the GLE70 was presumably not caused by the released energy from accelerated particles in the solar flare. Alternatively, the released energy from particle accelerations in solar radio emission type II burst concomitant coronal-mass-ejection-driven shocks seems to have been responsible for causing the GLE70.</P>
Firoz Khan,김재현 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.68 No.-
The effects of N doping concentration and dopant moieties on the electrochemical properties of nanoporous graphene and their dependence on annealing temperature are investigated. Four types of N moieties – amide, amine, graphitic-N, and oxidized-N – are obtained, which transformed into pyridinic-N and pyrrolic-N upon annealing. The diffusion coefficient (D′) of the ions in the electrode is the maximum at 400 °C because of a high level of N doping, whereas the second highest D′ value is obtained at 700 °C owing to a high level of reduction and N doping. The highest specific capacitance is obtained for the sample annealed at 400 °C.
Effect of Al Concentration on Photoluminescence Properties of Sol-Gel Derived Hydrogen Annealed ZnO
Firoz Khan,Sadia Ameen,Minwu Song,Mushahid Husain,Abdul Mobin,Hyung-Shik Shin 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.2
The effect of the Al/Zn atomic ratio on the photoluminescence properties of hydrogen annealed undoped and Al rich ZnO (AZO) films was studied. The Al/Zn atomic ratios in the AZO films were varied from 0to 40%. All the AZO films exhibited three peaks in the UV, green and red regions, whereas the undoped ZnO films had two peaks in the UV and green regions. The PL intensity in the UV and red regions increased with an increase in Al concentrations. The highest PL intensity in the UV region was observed in the 20% Al/Zn atomic ratio due to improvement in crystal quality which was also confirmed by XRD measurements. The PL emission in the red region was due to complex luminescent centers like (Vzn-Alzn)−. A blue shift was seen in the red region with the introduction of Al. The 20% AZO films obtained the strongest signal at ~420 cm−1, whereas no FTIR signal was observed at 420 cm−1 in undoped ZnO. The bond signature at ~420 cm−1 might be responsible for the highest PL intensity in NBE and red regions.
Correlation Between Reflectance and Photoluminescent Properties of Al-rich ZnO Nano-Structures
Firoz Khan,백성호,Nafis Ahmad,이건희,서태훈,서은경,김재현 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3
Al rich zinc oxide nano-structured films were synthesized using spin coating sol-gel technique. The films were annealed in oxygen ambient in the temperature range of 200-700 °C. The structural, optical, and photoluminescence (PL) properties of the films were studied at various annealing temperatures using X-ray diffraction spectroscopy, field emission scanning electron microscopy, photoluminescence emission spectra measurement, and Raman and UV-Vis spectroscopy. The optical band gap was found to decrease with the increase of the annealing temperature following the Gauss Amp function due to the confinement of the exciton. The PL peak intensity in the near band region (INBE) was found to increase with the increase of the annealing temperature up to 600 °C, then to decrease fast to a lower value for the annealing temperature of 700 °C due to crystalline quality. The Raman peak of E2 (low) was red shifted from 118 cm-1 to 126 cm-1 with the increase of the annealing temperature. The intensity of the second order phonon (TA+LO) at 674 cm-1 was found to decrease with the increase of the annealing temperature. The normalized values of the reflectance and the PL intensity in the NBE region were highest for the annealing temperature of 600 °C. A special correlation was found between the reflectance at λ = 1000 nm and the normalized PL intensity in the green region due to scattering due to presence of grains.
Firoz Ahmad,Md Meraj Uddin,Laxmi Goparaju 대한공간정보학회 2019 Spatial Information Research Vol.27 No.4
The present study examined the relationship among various diversified datasets using remote sensing and GIS. About 72% of the total forest area of Chhattisgarh state (59,935 km2) has shown a trend of negative change between the periods (1982 and 2006). Around 50% of the total forest fires of the state were found in the two tehsils of Narayanpur and Bijapur with two major forest fire hotspots. Approximately 86% of the total forest fire event of the state occurred in the category of ‘‘tropical mixed deciduous and dry deciduous forests’’ whereas the intensity of forest fire events was found 2.2 times in the category ‘‘tropical lowland forests, broadleaved, evergreen,\ 1000 m’’ when it was compared with the category of ‘‘tropical mixed deciduous and dry deciduous forests.’’ The highest poverty percent was found in the tehsil of Bijapur (65.9%) which retains a significantly high percentage of the tribal population (73.1%). The adaptive capacity of Raipur tehsil (state capital) is high whereas it reduces significantly towards north and south from the state capital. The climate anomaly data evaluation for the year 2030 showed variation such as reduction in rainfall and increase in temperature will significantly maneuver the forest fire regime in future is a matter of serious concern. The outcomes of the present study would certainly guide the policymakers of the state of Chhattisgarh to prepare a meaningful, transparent and robust plan for the betterment of people keeping in mind of future climate change impact.
Firoz Ahmed,권용주 한국교원대학교 뇌기반교육연구소 2022 Brain, Digital, & Learning Vol.12 No.4
This study was focused on the development of a graphic-based digital textbook for for Bangladesh’s higher secondary level student’s academic success and learning satisfaction in biology learning. In Bangladesh, the teaching method is traditionally traditional like a ‘Jug and Mug’, called teacher-centered learning; the instructor is at the center of all learning, and students are merely a listener. In the study, the researcher made an interactive digital textbook using Canva on human eyes to facilitate an interactive learning environment through various texts and activities to facilitate student-centered learning. Student-centered learning has not yet been introduced in Bangladesh. The data collection was carried out using the pretest-posttest control design. The researcher used both quantitative and qualitative methodologies in the experiment. The results indicate that the digital textbook is usable in the classroom despite of few infrastructural limitations and the experience digital textbook has been showed a high level of academic success.