Comparison of surface water flow simulation over structured and unstructured grids

Ajithkumar Nivedhitha,Verma Prabhakar Alok,Osei Frank B.,Shankar Hari 대한공간정보학회 2022 Spatial Information Research Vol.30 No.2

Structured grids have drawbacks such as cell distortion and artefacts leading to numerical accuracy reduction during simulations. Spatial support size had proven its importance in various estimation, and this is where unstructured grid comes into action. Performing geostatistical simulation on unstructured grid requires accounting of support size effect. In this article, two methods have been used for accounting the support size effect, one is the classical fine-scale simulation approach and the other approach is using Discrete Gaussian Model (DGM). Each method is applied to generate simulated Digital Elevation Model (DEM) (as used in this study) and the resultant DEMs are studied to understand the effect of spatial support size on surface flow estimation of water. It was observed that due to regularisation in the data of unstructured grid the flow velocity and water surface elevation of the unstructured DEM gave a similar behaviour than the structured DEM. The minimum RMSE for water surface elevation is 0.83 m for unstructured DEM while the minimum RMSE for flow discharge is 0.38 m3/s. The maximum coefficient of determination of flow channel velocity and water surface elevation is 0.709 and 0.86 respectively. The results suggested that the unstructured DEM generated using DGM approach shows a high correlation to reference DEM used in this study than the simulated structured DEM. The surface flow output it was inferred the flow variation in both structured and unstructured DEM is affected not only by the vertical resolution of DEM but also by the horizontal resolution.

Comparison of surface water flow simulation over structured and unstructured grids

Ajithkumar Nivedhitha,Verma Prabhakar Alok,Osei Frank B.,Shankar Hari 대한공간정보학회 2022 Spatial Information Research Vol.30 No.1

Structured grids have drawbacks such as cell distortion and artefacts leading to numerical accuracy reduction during simulations. Spatial support size had proven its importance in various estimation, and this is where unstructured grid comes into action. Performing geostatistical simulation on unstructured grid requires accounting of support size effect. In this article, two methods have been used for accounting the support size effect, one is the classical fine-scale simulation approach and the other approach is using Discrete Gaussian Model (DGM). Each method is applied to generate simulated Digital Elevation Model (DEM) (as used in this study) and the resultant DEMs are studied to understand the effect of spatial support size on surface flow estimation of water. It was observed that due to regularisation in the data of unstructured grid the flow velocity and water surface elevation of the unstructured DEM gave a similar behaviour than the structured DEM. The minimum RMSE for water surface elevation is 0.83 m for unstructured DEM while the minimum RMSE for flow discharge is 0.38 m3/s. The maximum coefficient of determination of flow channel velocity and water surface elevation is 0.709 and 0.86 respectively. The results suggested that the unstructured DEM generated using DGM approach shows a high correlation to reference DEM used in this study than the simulated structured DEM. The surface flow output it was inferred the flow variation in both structured and unstructured DEM is affected not only by the vertical resolution of DEM but also by the horizontal resolution.

Mass transfer kinetics using two-site interface model for removal of Cr(VI) from aqueous solution with cassava peel and rubber tree bark as adsorbents

M. Vasudevan,P. S. Ajithkumar,R. P. Singh,N. Natarajan 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.2

Present study investigates the potential of cassava peel and rubber tree bark for the removal of Cr (VI) from aqueous solution. Removal efficiency of more than 99% was obtained during the kinetic adsorption experiments with dosage of 3.5 g/L for cassava peel and 8 g/L for rubber tree bark. By comparing popular isotherm models and kinetic models for evaluating the kinetics of mass transfer, it was observed that Redlich-Peterson model and Langmuir model fitted well (R2 > 0.99) resulting in maximum adsorption capacity as 79.37 mg/g and 43.86 mg/g for cassava peel and rubber tree bark respectively. Validation of pseudo-second order model and Elovich model indicated the possibility of chemisorption being the rate limiting step. The multi-linearity in the diffusion model was further addressed using multi-sites models (two-site series interface (TSSI) and two-site parallel interface (TSPI) models). Considering the influence of interface properties on the kinetic nature of sorption, TSSI model resulted in low mass transfer rate (5% for cassava peel and 10% for rubber tree bark) compared to TSPI model. The study highlights the employability of two-site sorption model for simultaneous representation of different stages of kinetic sorption for finding the rate-limiting process, compared to the separate equilibrium and kinetic modeling attempts.

Isolation and Identification of Cytotoxic and Biological Active Toxin from the Puffer Fish Arothron stellatus

Veeruraj, Anguchamy,Pugazhvendan, Sampath Renuga,Ajithkumar, Thipramalai Thankappan,Arumugam, Muthuvel Korean Society of ToxicologyKorea Environmental Mu 2016 Toxicological Research Vol.32 No.3

This study is to investigate the biological, biochemical and cytotoxic effects of puffer fish (Arothron stellatus) toxin extracts under in-vitro condition. Extracted toxins from various organs of puffer fish were purified by using active charcoal column, and Bio-gel-P2 column chromatography. The lethality of toxin was tested in crabs, which consists of neurotoxic compounds. The degree of the brine shrimp lethality assay was found directly proportional to the concentration of the toxin extracts, which was well supported by hemolytic assay. The experimental results suggested that the gonad was found higher toxins than the liver and muscles. The mortality rate of brine shrimp nauplii was increased with the raise of concentrations of toxin level. Among the different doses and time dependent cytotoxic effect of human cervical carcinoma (HeLa) cells were showed $4.0{\mu}g/mL$ of toxin, which was effectively inhibited cancer cell proliferation. HPLC and TLC analysis was revealed that the A. stellatus toxin contains tetrodotoxin (TTX), related compounds 4-epi TTX and anhydro-TTX. The present results suggested that the A. stellatus contain TTX as a major and anh-TTX as a minor toxin. It could be the potential candidate in the field of anticancer drug discovery against human cervical cancer cells. The present data is confirming that the puffer fish toxin as an interesting source of novel bioactive natural compounds with potent applications in pharmacology.

Synthesis, Characterization, and Fabrication of Hydrophilic Antimicrobial Polymer Thin Film Coatings

Akshatha Nagaraja,Yashoda Malgar Puttaiahgowda,Ananda Kulal,Ajithkumar Manayan Parambil,Thivaharan Varadavenkatesan 한국고분자학회 2019 Macromolecular Research Vol.27 No.3

An efficient hydrophilic-antimicrobial thin film coating of functionalized polymaliamides for controlling pathogenic microorganisms is reported in this article. The article is enriched with synthesis, characterization and antimicrobial studies of polymaliamides and its thin film. FTIR, 1H NMR, 13C NMR details of the polymaliamidesis explicated,and the thermal properties of the polymer are revealed using TGA, DSC studies and detailed explanation is provided in the article. The activity of the polymer and thin film against Staphylococcus aureus, Escherichia coli, tuberculosis variant bacteria Mycobacterium smegmatis and Candida albicans are also reported ornately. The morphological behavior of film when interacting with the microbes is studies using SEM and AFM studied and presented elaborately.

An experimental investigation on upward solar air heater with impinging air jets

M. Harikrishnan,R. Ajith Kumar,S. Ajithkumar,Rajesh Baby 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

This study presents and discuss the results of an experimental investigation conducted to understand and quantify the impact of air mass flow rate(m) over the heat transfer attributes of an upward solar air heater (SAHRR) utilizing impinging air jets. Experimental investigation was carried out for various mass flow rates ranging from 0.008 to 0.024 kg/s for various impinging air jet diameters (4, 6 and 8 mm). The thermal performance was evaluated based on the average value of Nusselt number, first law thermal efficiency, thermohydraulic efficiency and exergy efficiency. The lowest and the highest first law efficiency for an upward SAHRR employing 6 mm diameter jet is between 44 % and 88 %, respectively, when the solar radiation maintained is 1000 W/m 2 . Moreover, the final outcomes are compared with the base model (SAHRR without jet impingement) in order to highlight the positive impact of jet impingement on the performance of SAHRR.

Enhanced light harvesting with chromium in NaLu_0.70−xGd_0.10F₄:Yb_0.18Er_0.02Cr_x (0≤x≤0.25) upconversion system

Huy, Bui The,Gerelkhuu, Zayakhuu,Chung, Jong Won,Dao, Van-Duong,Ajithkumar, Gangadharan,Lee, Yong-Ill Elsevier 2017 Materials science and engineering B. Advanced Func Vol.223 No.-

<P>Cr3+-doped Nalm(0.70-x)Gd(0.10)F(4):Yb0.18Er0.02Crx nanoparticles were synthesized by one step solvothermal method. The structural, emission properties were studied by XRD, FT-IR, emission spectra. The doping of 15 mol% Cr3+ into NaLu0.70-xGd0.10F4:Yb0.18Er0.02Crx induced cubic-hexagonal phase transition, with a consequent 20 times improvement in the upconversion fluorescence quantum yield. The roles of Cr3+ in the phase transition as well as the mechanism of the multi-photon upconversion process in the material were discussed. The Yb3+-Cr3+ dimer could play the role of as a sensitizer by transferring energy to Er3+. The Cr3+ ions result an asymmetry in the environment surrounding the rare-earth ions, which would favor the hypersensitive transitions. This research may open up a new perspective to prepare high upconversion luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.</P>