Determination of surface properties and Gutmann’s Lewis acidity–basicity parameters of thiourea and melamine polymerized graphitic carbon nitride sheets by inverse gas chromatography

Sreekanth, T.V.M.,Basivi, Praveen Kumar,Nagajyothi, P.C.,Dillip, G.R.,Shim, J.,Ko, T.J.,Yoo, K. Elsevier 2018 Journal of chromatography Vol.1580 No.-

<P><B>Abstract</B></P> <P>Melamine and thiourea-derived graphitic carbon nitrides (M-GCN/T-GCN) were synthesized and characterized. The surface properties were investigated using inverse gas chromatography (IGC) and compared. Net retention volumes of M-GCN and T-GCN were measured with <I>n</I>-alkanes (C<SUB>5</SUB>–C<SUB>10</SUB>) and polar probes. The London dispersive surface free energies ( γ s d ), calculated using Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific components of the enthalpy and entropy of adsorption for the polar probes were obtained using the Schultz, Dong, and Sawyer–Brookman methods. The Gutmann’s Lewis acid–base parameters, <I>K<SUB>a</SUB> </I> and <I>K<SUB>b</SUB> </I>, were determined using the surface free energy ( Δ G a S ) via these methods. The surface character ‘<I>S’</I> values (<I>K<SUB>b</SUB> </I>/<I>K<SUB>a</SUB> </I>) of M-GCN and T-GCN using the respective methods are 4.04, 3.78, and 5.08 and 4.11, 5.27, and 2.86. Hence, the surfaces contain more basic than acidic sites and could interact strongly with acidic media. Thus, IGC elucidates the surface charges of the GCN matrix resulting from surface chemical modification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphitic carbon nitride was synthesized using two precursors, melamine and thiourea. </LI> <LI> Physicochemical properties were confirmed by XRD, XPS and BET. </LI> <LI> Inverse gas chromatography was employed to understand surface free energy of GCN. </LI> <LI> The London dispersive parameters were determined by Schultz/Dorris–Gray methods. </LI> <LI> The Lewis acid–base parameters, showing the more basic character of GCN. </LI> </UL> </P>

Comparative study of finite element analysis and generalized beam theory in prediction of lateral torsional buckling

Sharma, Shashi Kant,Kumar, K.V. Praveen,Akbar, M. Abdul,Rambabu, Dadi Techno-Press 2022 Advances in materials research Vol.11 No.1

In the construction industry, thin-walled frame elements with very slender open cross-sections and low torsional stiffness are often subjected to a complex loading condition where axial, bending, shear and torsional stresses are present simultaneously. Hence, these often fail in instability even before the yield capacity is reached. One of the most common instability conditions associated with thin-walled structures is Lateral Torsional Buckling (LTB). In this study, a first order Generalized Beam Theory (GBT) formulation and numerical analysis of cold-formed steel lipped channel beams (C80×40×10×1, C90×40×10×1, C100×40×10×1, C80×40×10×1.6, C90×40×10×1.6 and C100×40×10×1.6) subjected to uniform moment is carried out to predict pure Lateral Torsional Buckling (LTB). These results are compared with the Finite Element Analysis of the beams modelled with shell elements using ABAQUS and analytical results based on Euler's buckling formula. The mode wise deformed shape and modal participation factors are obtained for comparison of the responses along with the effect of varying the length of the beam from 2.5 m to 10 m. The deformed shapes of the beam for different modes and GBTUL plots are analyzed for comparative conclusions.

X-Band Dielectric Characterization and Microwave Absorption Characteristics of Polyaniline Loaded Poly Vinyl Butyral (PVB)

M. Praveen Kumar,Sarika Raga,S. Chetana,Dinesh Rangappa 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.1

Conducting polymer-based materials received tremendous attraction in the area of microwave absorption due to their effective microwave dielectric properties. In this work, conducting polymer polyaniline (PANI) loaded polyvinyl butyral (PVB) for X-band (8.2–12.4 GHz) dielectrics and absorption characteristics are studied. Electromagnetic (EM) performances for diff erent solution processed PANI loaded (4–16 wt%) PVB-PANI are investigated and optimized the filler (PANI) loading in PVB matrix for the microwave absorption. The study reveals that the presence of PANI in PVB significantly improves the different EM properties. The minimum reflection loss (RL) value − 10 dB (corresponds to 90% absorption) is achieved for 8 wt% PANI loaded PVB (4 mm). The RL ≤ − 10 dB is achieved at minimum thickness 2–3 mm for 10–16 wt% PANI loading. The RL value − 30 dB is obtained for 2.5 mm thicker 16 wt% PANI loaded PVB with an excellent absorption bandwidth, indicating a superior result for real time application compared to other polymer nanocomposites.

Evaluation of Strong Microwave Absorption Property of PVB-PEDOT:PSS-Ti3C2Tx MXene Nanocomposite With Materials Data-Driven Discovery

M. Praveen Kumar,Sarika Raga,S. Chetana,K. Avinash,Arjun Dey,Dinesh Rangappa 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.3

2D nanomaterial, especially 2D metal carbides or MXene loaded polymer nanocomposite is highly valued electromagnetic material. In this work, Ti3C2TX MXene loaded polyvinyl butyral (PVB)-Poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS)-Ti3C2TX MXene nanocomposite is explored for microwave absorption in the frequency range of X-Band and Ku-Band (8.2–18 GHz). The reflection loss (RL) of the optimized PEDOT:PSS content PVB-PEDOT:PSS was found to improve significantly in presence of the Ti3C2TX MXene viz., 5%, 10%, 20% and 40%. Ti3C2TX MXene loaded solution processed PVB-PEDOT:PSS-Ti3C2TX MXene indicates RL is strongly effected by Ti3C2TX MXene loading. To optimize Ti3C2TX MXene content in PVB-PEDOT:PSS-Ti3C2TX MXene nanocomposite for best RL with minimum thickness, the materials data-driven discovery was used for which experimental data sets were used as input parameters. Through the materials data-driven discovery, the minimum RL value -63 dB was predicted at 2.6 mm for 18 wt% Ti3C2TX MXene loaded PVB-PEDOT:PSS-Ti3C2TX MXene nanocomposite which was not examine before. The predicted RL data for the optimized PVB-PEDOT:PSS-Ti3C2TX MXene nanocomposite (18 wt% MXene content) was compared with the experimental data.

On-Chip Spiral Inductors and On-Chip Spiral Transistors for Accurate Numerical Modeling

M. Dhamodaran,R. Praveen Kumar,S. Jegadeesan 한국자기학회 2018 Journal of Magnetics Vol.23 No.1

This paper presents a new model for designing on-chip spiral inductor and on-chip spiral transistors. For this, the coupling between on-chip inductors and transistors has been implemented. The electromagnetic coupling between the inductors and the transistors and the mutual inductance are modeled by presenting the magnetic vector potential to study the coupling effect. It changes the surface integral of the magnetic field into the loop integral of the magnetic vector potential to calculate the coupling. In this method, the partial mutual inductance idea to compute the mutual inductance between two conductor sections instead of conductor loops can be developed. The inductance classification is applied to an on-chip environment to characterize interconnects and integrated inductors. The investigative model is reconsidered to incorporate the semiconductor substrate losses and the skin effect. The numerical solutions of the investigative model are also presented. To simulate the proposed model ADS Momentum software is used.

Artificial Neural Network Model for Rainfall-Runoff - A Case Study

P.Sundara Kumar,T.V.Praveen,M. Anjanaya Prasad 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.3

Soft computing models like Artificial Neural Network (ANN) have been widely used to model complex hydrological processes, such as rainfall-runoff and have been reported to be one of the promising tools in hydrology. In this paper, the influences of back propagation algorithm and their efficiencies which affect the input dimensions on rainfall runoff model have been demonstrated. The capability of the Artificial Neural Network with different input dimensions have been attempted and demonstrated with a case study on Sarada River Basin. The developed ANN models were able to map relationship between input and output data sets used. The developed model on rainfall and runoff pattern have been calibrated and validated. The significant input variables for training of ANN models were selected based on statistical parameters viz. cross-correlation, autocorrelation, and partial autocorrelation function. Various combinations were attempted and six combinations were selected based on the statistics of these functions. It was found those models considering rainfall lag rainfall and lag discharge as inputs were performing better than those considering rainfall alone. It was found that the neural network model developed is performing well. It can be inferred from the developed model, Neural Network model was able to predict runoff from rain fall data fairly well for a small semi-arid catchment area considered in the present study.

Role of Peroral Endoscopic Myotomy in Advanced Achalasia Cardia With Sigmoid and/or Megaesophagus: A Systematic Review and Metanalysis

( Harshal S Mandavdhare ),( Praveen Kumar M ),( Jayendra Shukla ),( Antriksh Kumar ),( Vishal Sharma ) 대한소화기기능성질환·운동학회 2022 Journal of Neurogastroenterology and Motility (JNM Vol.28 No.1

Background/Aims Sigmoid esophagus and/or megaesophagus are considered as an advanced stage in the natural history of achalasia cardia. The role of peroral endoscopic myotomy (POEM) in these subset of patients is emerging. We performed a systematic review and metanalysis to study the efficacy of POEM in advanced achalasia cardia with sigmoid and megaesophagus. Methods A literature search in PubMed and Embase was done from inception till August 3, 2021 to look for studies reporting exclusively on the role of POEM in advanced achalasia cardia with sigmoid and/or megaesophagus. The random effect method with inverse variance approach was used for the computation of pooled prevalence. For 2 groups’ analysis of continuous outcome standardized mean difference was used as the summary measure. Results Eleven studies with 428 patients were included for analysis. The pooled technical and clinical success was 98.27% (95% CI, 96.19- 99.22; I² = 0%) and 89.38% (95% CI, 84.49-92.86; I² = 26%) and on subgroup analysis into sigmoid and megaesophagus it was (98.06% [95% CI, 95.41-99.19; I² = 0%], 98.47% [95% CI, 92.72-99.69; I² = 0%] and 87.92% [95% CI, 80.68-92.70; I² = 37%], 88.36% [95% CI, 62.62-97.17; I² = 77%]) respectively. The clinical success at < 1 year and 1-3 year follow-up was 89.37% (95% CI, 82.82-93.61; I² = 0%) and 88.66% (95% CI, 81.65-91.22; I² = 46%) respectively. There was a significant reduction in the post-POEM scores with standardized mean difference for Eckardt score (4.81), for integrated relaxation pressure at 4 seconds (1.93), and for lower esophageal sphincter pressure (2.06). Conclusions POEM is an effective modality of treatment even in the subset of patients of advanced achalasia cardia with sigmoid and megaesophagus. (J Neurogastroenterol Motil 2022;28:15-27)

Clinical presentation of COVID-19 in patients with inflammatory bowel disease: a systematic review and meta-analysis

( Anupam K. Singh ),( Anuraag Jena ),( Praveen Kumar-m ),( Daya Krishna Jha ),( Vishal Sharma ) 대한장연구학회 2022 Intestinal Research Vol.20 No.1

Background/Aims: Coronavirus disease 2019 (COVID-19) is recognized to have variable clinical manifestations. The clinical presentation of patients with inflammatory bowel disease (IBD) having COVID-19 is unclear. Methods: We identified articles reporting about the clinical presentation of COVID-19 in those with underlying IBD from PubMed and Embase. The studies, irrespective of design or language, were included. The overall pooled frequency of various symptoms was estimated. Joanna Briggs Institute Critical appraisal checklist was used to assess the quality of studies. Results: Eleven studies, including 1,325 patients, were included in the pooled analysis. The pooled estimates for clinical presentation were; fever: 67.53% (95% confidence interval [CI], 45.38-83.88), cough: 59.58% (95% CI, 45.01-72.63), diarrhea: 27.26% (95% CI, 19.51-36.69), running nose: 27% (95% CI, 15.26-43.19) and dyspnea: 25.29% (95% CI, 18.52-33.52). The pooled prevalence rates for abdominal pain, nausea and vomiting were 13.08% (95% CI, 9.24-18.19), 10.08% (95% CI, 5.84-16.85) and 8.80% (95% CI, 4.43-16.70) per 100 population, respectively. Conclusions: The clinical presentation of COVID-19 in IBD patients is similar to the general population. (Intest Res 2022;20:134-143)

Impact of diabetes mellitus on morbidity and survival after pancreaticoduodenectomy for malignancy

Kunal Bikram Deo,Aditya Atul Kulkarni,Praveen Kumar-M,Gautham Krishnamurthy,Sunil Shenvi,Surinder Singh Rana,Rakesh Kapoor,Rajesh Gupta 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.2

Backgrounds/Aims: Diabetes mellitus (DM) is a known risk factor for morbidity, length of hospital stay, or mortality after surgery, however, its impact on postoperative course and long-term survival after pancreaticoduodenectomy (PD) is not clear. Methods: This is a retrospective analysis of prospectively maintained database of 141 patients with periampullary and pancreatic head adenocarcinoma operated between January 2001 and March 2019. Clinico-pathological records and follow-up data were retrieved and analyzed. Cumulative hazard was computed for comparing the survival between DM and non-DM. Results: DM was present in 31/141 (21.9%) patients, while 16/31 (51.6%). were new-onset DM (NODM). Tumor size, lymphovascular & perineural invasion, type of surgery, lymph node positivity and R0 resection rate were comparable between diabetic and non-diabetic. There was no significant difference in postoperative pancreatic fistula, delayed gastric emptying, infectious complication, hospital stay and mortality between DM and non-diabetics. Patients with DM had worse survival at 3 years (OS: HR, 3.11 [1.43-6.76] p=0.004, DFS: HR, 2.61 [1.23-5.53] p=0.01) and 5 years (OS: HR, 3.32 [1.46-7.53] p=0.004, DFS: HR, 2.87 [1.29-6.41] p=0.009). On multivariate analysis, DM (3 year OS: HR, 2.61 [1.14-5.98] p=0.022, DFS: HR, 2.19; p=0.058) (5 year OS: HR, 2.55; p=0.04, DFS: HR, 2.25; p=0.068) and pylorus resecting surgery were significantly associated with worse survival at 3 and 5 years. Conclusions: Preoperative DM has no significant effect on postoperative course but has negative impact on 3-year and 5-year OS and DFS after PD for pancreatic and periampullary adenocarcinoma.

Effect of Stack Spacing on the Performance of Thermoacoustic Refrigerators Using Helium and Air as Working Substances

B. G. PRASHANTHA,S. SEETHARAMU,G. S. V. L. NARASIMHAM,M. R. Praveen Kumar 대한설비공학회 2019 International Journal Of Air-Conditioning and Refr Vol.27 No.2

This paper deals with the design of thermoacoustic refrigerators using linear thermoacoustic theory. The refrigerator components are designed at 3% drive ratio by considering the practical limitations of providing sufficient spacing for attaching the loudspeaker to the resonator tube and accommodating instrumentation. The effects of spiral stack spacing in terms of thermal penetration depth on the theoretical performance of refrigerator using helium and air as working substances are discussed. The quarter-wavelength resonator designs with taper and divergent section terminated with hemispherical end are optimized with helium and air for better performance. Theoretical results are validated with DeltaEC software results and are in agreement with each other. Helium shows better performance compared to air but lacks power density. The DeltaEC predicts COP 0.514 at the cold heat exchanger temperature of −30∘C with helium compared to air (COP 0.616 at8.8∘C) for the 50 W cooling power 100 mm diameter quarter-wavelength resonator designs.