Microwave-assisted production of activated carbons from oil palm shell in the presence of CO2 or N2 for CO2 adsorption

Roozbeh Hoseinzadeh Hesas,Arash Arami-Niya,Wan Mohd Ashri Wan Daud,J.N. Sahu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-

Activated carbon (AC) was prepared from oil palm shell using different ratios of KOH as an activation agent and various microwave irradiation powers. To study the effects of physical agents, the impregnated precursors were activated under a flow of CO2 or N2. Maximum BET surface areas of 1196 and 1630 m2/g were achieved in the presence of CO2 and N2, respectively. The textural properties of the samples with the highest surface areas were investigated using ultimate and proximate analyses, SEM and FTIR. The CO2 adsorption results suggest that the ACs are promising adsorbents for gas separation or storage applications.

Optimization of ammonia production from urea in continuous process using ASPEN Plus and computational fluid dynamics study of the reactor used for hydrolysis process

J.N. Sahu,V.S. Rama Krishna Chava,Shadab Hussain,A.V. Patwardhan,B.C. Meikap 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.4

The present study addresses the methods and means to safely produce relatively small amounts (i.e., up to 50 kg/h) of ammonia. The optimization and simulation study conducted for continuous process and effect of operation conditions like reaction temperature, initial feed concentration and pressure on ammonia production carried out using ASPEN Plus. Also, a computational fluid dynamics (CFD) model was proposed to simulate the hydrolysis of urea for synthesis of ammonia. A series of parametric studies to investigate flow rates, thermal boundary conditions and reactor geometry was performed for hydrolysis of urea and the optimized operating conditions and reactor geometry were obtained. Detailed three-dimensional flow, heat and chemistry simulations of ammonia, carbon dioxide and ammonium carbamate. The study demonstrates that simulation is a useful tool for diagnosing hydrolysis reactor mixing pathologies and for identifying practical countermeasures that could improve process performance.

An overview on methods for the production of carbon nanotubes

N.M. Mubarak,E.C. Abdullah,N.S. Jayakumar,J.N. Sahu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

Carbon nanotubes (CNTs) are one of the most exciting discoveries in nanoscale sciences. A brief survey of experimental work directed towards the synthesis of CNTs has been discussed. The various methods of production of CNTs are explained outlining their capabilities, efficiencies and possible exploitation as economic large scale production. Among the discussed techniques, the chemical vapor deposition (CVD) appears to be the most potential way to produce high quality of CNTs at high yield. The advantages of CVD over other techniques are also explained and the effects of process parameter on the synthesis of these nanomaterials are discussed.

Microwave assisted multiwall carbon nanotubes enhancing Cd(II) adsorption capacity in aqueous media

N.M. Mubarak,J.N. Sahu,E.C. Abdullah,N.S. Jayakumar,P. Ganesan 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-

Novel multiwall carbon nanotubes (MWCNTs) have been successfully synthesized using tubular microwave chemical vapour deposition technique and proved to be an outstanding adsorbent for the removal of Cd(II) from aqueous solution. The effect of process parameters such as pH, MWCNTs dosage, agitation speed and time were investigated. The maximum adsorption capacities of Cd(II) were found to be 88.62 mg/g and a statistical analysis reveals that the optimum conditions for the highest removal (98%) of Cd(II) are at pH 5, MWCNTs dosage 0.1 g, agitation speed and time of 160 rpm and 50 min, respectively with the initial concentration of 10 mg/L. The Langmuir and Freundlich isotherm models match the experimental data very well and adsorption kinetic obeyed pseudo-second order. Our results proved that MWCNTs can be used as an effective Cd(II) adsorbent due to the high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.

The Horizontal Branch Population of NGC 1851 as Revealed by the Ultraviolet Imaging Telescope (UVIT)

Subramaniam, Annapurni,Sahu, Snehalata,Postma, Joseph E.,Cô,té,, Patrick,Hutchings, J. B.,Darukhanawalla, N.,Chung, Chul,Tandon, S. N.,Rao, N. Kameswara,George, K.,Ghosh, S. K.,Girish, V.,M American Astronomical Society 2017 The Astronomical journal Vol.154 No.6

<P>We present the UV photometry of the globular cluster NGC 1851 using images acquired with the Ultraviolet Imaging Telescope (UVIT) onboard the ASTROSAT satellite. Point-spread function fitting photometric data derived from images in two far-UV (FUV) filters and one near-UV (NUV) filter are used to construct color-magnitude diagrams (CMDs), in combination with HST and ground-based optical photometry. In the FUV, we detect only the bluest part of the cluster horizontal branch (HB); in the NUV, we detect the full extent of the HB, including the red HB, blue HB, and a small number of RR Lyrae stars. UV variability was detected in 18 RR Lyrae stars, and three new variables were also detected in the central region. The UV/optical CMDs are then compared with isochrones of different age and metallicity (generated using Padova and BaSTI models) and synthetic HB (using helium-enhanced Y2 models). We are able to identify two populations among the HB stars, which are found to have either an age range of 10-12. Gyr, or a range in Y-ini of 0.23-0.28, for a metallicity of [Fe/H] = -1.2 to -1.3. These estimations from the UV CMDs are consistent with those from optical studies. The almost-complete sample of the HB stars tends to show a marginal difference in spatial/azimuthal distribution among the blue and red HB stars. Thus, this study showcases the capability of UVIT, with its excellent resolution and large field of view, to study the hot stellar population in Galactic globular clusters.</P>

Multi-kilowatt Single-mode Ytterbium-doped Large-core Fiber Laser

정윤찬,Johan Nilsson,David N. Payne,Alexander J. Boyland,Jayanta K. Sahu,정승환 한국광학회 2009 Current Optics and Photonics Vol.13 No.4

We have demonstrated a highly efficient cladding-pumped ytterbium-doped fiber laser, generating >2.1 kW of continuous-wave output power at 1.1 μm with 74% slope efficiency with respect to launched pump power. The beam quality factor (M2) was better than 1.2. The maximum output power was only limited by available pump power, showing no evidence of roll-over even at the highest output power. We present data on how the beam quality depends on the fiber parameter, based on our current and past fiber laser developments. We also discuss the ultimate power-capability of our fiber in terms of thermal management, Raman nonlinear scattering, and material damage, and estimate it to 10 kW.

Temporal variations of black carbon in Guangzhou, China, in summer 2006

Verma, R. L.,Sahu, L. K.,Kondo, Y.,Takegawa, N.,Han, S.,Jung, J. S.,Kim, Y. J.,Fan, S.,Sugimoto, N.,Shammaa, M. H.,Zhang, Y. H.,Zhao, Y. Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.14

<P>Abstract. In situ measurements of the mass concentration of black carbon (BC) and mixing ratios of carbon monoxide (CO) and carbon dioxide (CO2) were made at Guangzhou, an urban measurement site in the Pearl River Delta (PRD), China, in July 2006. The average ± standard deviation (SD) concentrations of BC, CO, and CO2 were 4.7± 2.3 μgC m−3, 798± 459 ppbv, and 400± 13 ppmv, respectively. The trends of these species were mainly controlled by synoptic-scale changes in meteorology during the campaign. Based on back trajectories, data are analyzed separately for two different air mass types representing northerly and southerly flows. The northerly air masses, which constituted ~25% of the campaign, originated mostly in the PRD and hence represent observations on regional scales. On the other hand, during southerly flow (~75%), the measurements were influenced by dilution due to cleaner marine air. The diurnal patterns of BC, CO, and CO2 exhibited peak concentrations during the morning and evening hours coinciding with rush-hour traffic. The ratios of OC/BC were lower during the morning hour peaks in the concentrations of primary pollutants due to their fresh emissions mainly from vehicular traffic in Guangzhou. The diurnal variations of BC observed in southerly air masses tended to follow the traffic patterns of heavy-duty vehicles (HDV) in Guangzhou, while the roles of other sources need to be investigated. The slopes of ΔBC/ΔCO, ΔBC/ΔCO2, and ΔCO/ΔCO2 observed during northerly flows were 0.0045 μgC m−3/ppbv, 0.13 μgC m−3/ppmv, and 49.4 ppbv/ppmv, respectively, agreeing reasonably with their respective emission ratios derived from regional emission inventories. </P>

Unifying darko-lepto-genesis with scalar triplet inflation

Arina, C.,Gong, J.O.,Sahu, N. North Holland 2012 Nuclear Physics, Section B Vol.865 No.3

We present a scalar triplet extension of the standard model to unify the origin of inflation with neutrino mass, asymmetric dark matter and leptogenesis. In presence of non-minimal couplings to gravity the scalar triplet, mixed with the standard model Higgs, plays the role of inflaton in the early Universe, while its decay to SM Higgs, lepton and dark matter simultaneously generate an asymmetry in the visible and dark matter sectors. On the other hand, in the low energy effective theory the induced vacuum expectation value of the triplet gives sub-eV Majorana masses to active neutrinos. We investigate the model parameter space leading to successful inflation as well as the observed dark matter to baryon abundance. Assuming the standard model like Higgs mass to be at 125-126 GeV, we found that the mass scale of the scalar triplet to be @?O(10<SUP>9</SUP>) GeV and its trilinear coupling to doublet Higgs is @?0.09 so that it not only evades the possibility of having a metastable vacuum in the standard model, but also lead to a rich phenomenological consequences as stated above. Moreover, we found that the scalar triplet inflation strongly constrains the quartic couplings, while allowing for a wide range of Yukawa couplings which generate the CP asymmetries in the visible and dark matter sectors.

Microwave induced synthesis of magnetic biochar from agricultural biomass for removal of lead and cadmium from wastewater

M.W. Yap,N.M. Mubarak,J.N. Sahu,E.C. Abdullah 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

The novel magnetic biochar (MB) has been successfully synthesized by using the microwave technique,using discarded materials such as coconut shell (CS). The optimized conditions for the best novelmagnetic biochar synthesis are at 800 W reaction power, 20 min reaction time, and 0.5 g (FeCl3:biomass)impregnation ratio. The detailed physical and chemical analyses of novel magnetic biochar were found tobe in good agreement with the hypothesis. These newly produced magnetic biochars have high surfacearea of 834 m2/g and this leads to high efficiency in the removal of cadmium and lead from wastewater. The results revealed that magnetic biochar composite exhibited excellent ferromagnetic property with asaturation magnetization of 6 emu/g. As for new invention, the magnetic biochar can be directlyproduced using microwaves heating by single stage of activation compared to the conventional method.

Optimization of Bioreactor Profile Control

Ubaid Imtiaz,Sudhanshu S. Jamuar,J. N. Sahu 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10

The use of Nonlinear Autoregressive? moving average (NARMA) neuro controller for temperature control and two degree of freedom (2DOF) PID controllers also known as the ISA-PID controllers for pH and dissolved oxygen control of a biochemical reactor has been presented in this paper. The process model for yeast fermentation has been described in terms of temperature, pH and dissolved oxygen. The NARMA neuro controller has been trained by Levenberg-Marquardt training algorithm. The ISA-PID controllers have been tuned by MATLAB’s auto tune feature along with manual tuning. Random profiles have been used for simulation. The performance of the controllers for following desired random profiles has been shown in contrast to the anti-windup PID (AWU-PID) controllers. The NARMA neuro controller and the ISA-PID controllers have shown overall improvement in controlling the process.