Micro and macro in the dynamics of dilute polymer solutions: Convergence of theory with experiment

Prakash, J. Ravi The Korean Society of Rheology 2009 Korea-Australia rheology journal Vol.21 No.4

Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multi scale simulations is discussed.

Improved resistive switching performance in Cu-cation migrated MoS2 based ReRAM device incorporated with tungsten nitride bottom electrode

Ravi Prakash,Shubham Sharma,Anuj Kumar,Davinder Kaur 한국물리학회 2019 Current Applied Physics Vol.19 No.3

The resistive switching characteristics of sputtered deposited molybdenum disulphide (MoS2) thin film has been investigated in Cu/MoS2/W2N stack configuration for Resistive Random Access Memory (ReRAM) application. The benefits of incorporating tungsten nitride (W2N) as a bottom electrode material were demonstrate by stability in operating voltages, good endurance (103 cycles) and long non-volatile retention (103 s) characteristics. Resistive switching properties in Cu/MoS2/W2N structure are induced by the formation/disruption of Cu conducting filaments in MoS2 thin film. Ohmic law and space charge limited current (SCLC) are observed as dominant conduction mechanism in low resistance state (LRS) and high resistance state (HRS) respectively. This study suggests the application of MoS2 thin films with W2N bottom electrode for next generation non-volatile ReRAM application.

Micro and macro in the dynamics of dilute polymer solutions: Convergence of theory with experiment

J. Ravi Prakash 한국유변학회 2009 Korea-Australia rheology journal Vol.21 No.4

Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multiscale simulations is discussed.

Study of Dark-Conductivity and Photoconductivity of ZnO Nano Structures Synthesized by Thermal Decomposition of Zinc Oxalate

Ravi Shankar,Rajneesh K Srivastava,S.G. Prakash 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5

In the present work, zinc oxalate [ZnC2O4·2H2O] was used as precursor to prepare zinc oxide nano structures by thermal decomposition. Its photoconductivity and dark-conductivity properties have been studied in air as well as in vacuum. Voltage dependence of photocurrent and dark-current has been observed at room temperature in air under UV-vis illumination and is found as superlinear in nature. Rise and decay curve in air exhibits anomalous behavior wherein the photocurrent decreases even during steady illumination. In vacuum,the rise of photocurrent becomes slow and prolonged.

Association of Circulating Brain-Derived Neurotrophic Factor with Cognition among Adult Obese Population

Ravi Babu Katuri,Girwar Singh Gaur,Jaya Prakash Sahoo,Zachariah Bobby,Karthik Shanmugavel 대한비만학회 2021 The Korean journal of obesity Vol.30 No.2

Background: Obesity has a strong association with the risk of developing cognitive impairment and dementia at a later age. Brain-derived neurotrophic factor (BDNF) and its receptor appear to be important components in cognitive function and are also involved in energy homeostasis. The level of circulating BDNF and its association with cognition has yet to be delineated clearly. In this work we studied the association of circulating BDNF with cognition among the adult obese population. Methods: The study involved 132 healthy participants between 18 and 40 years of age and of both sexes. The participants were categorized into an obesity group (n=66) and a non-obese group (n=66) based on their body mass index (Asian criteria). The level of cognitive performance was assessed by the event-related potentials P300 (ERPs-P300), mini-mental state examination (MMSE), both visual and auditory reaction times (VRT and ART, respectively), and other pen and paper tests related to memory and executive function. Serum BDNF, glycemic and lipid profiles were estimated. Results: We found significant differences in the ERPs-P300 latency (P<0.001) and amplitude (P=0.002) between the non-obese and obese group. The MMSE score was significantly reduced while VRT (P=0.005) and ART (P=0.001) were larger in the obese group. BDNF levels (P<0.001) were significantly reduced and negatively associated with the obese group. ERPs-P300 latency was negatively associated (r=–0.674, P=0.001) whereas amplitude (r=0.507, P<0.001) was positively associated with the BDNF levels in the adult obese population. Conclusion: We found reduced circulating BDNF levels in obese adults and that lower BDNF levels were strongly associated with cognitive decline in the obese adult population.

Prediction of weld zone shape with effect of tool pin profile in friction stir welding process

Prashant Prakash,Ravi Shankar Anand,Sanjay Kumar Jha 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

This article investigates the effect of tool pin profile on weld zone shape using computational fluid dynamics techniques in friction stir welding process. The effect of tool pin profile on weld zone shape was investigated by four different pin profile tools: Cylindrical, conical, cylindrical-conical and stepped-conical. In the numerical simulation process, workpiece material and tool are considered as non-Newtonian fluids and solid material, respectively. And simulation is carried out under transient state condition. Temperature distribution and material flow profile developed by the tool pin profile are analyzed for the understanding of viscosity profile of the weld zone region. Critical iso-viscosity surface is developed from the viscosity profile to determine the difference between deformed and undeformed material, which is finally used to determine the weld zone shape. The simulation result shows that maximum temperature and material flow velocity are produced by stepped-conical pin profile tool with respect to all other tools. It is observed from the iso-viscosity surface analysis that a vaseshaped geometry developed around the contact region of the tool and workpiece. The weld zone shape produced by stepped-conical pin profile tool is cylinder dominant vase shape, and weld zone shape of all other tools is basin dominant vase shape. Numerical model was also validated with experimental results of temperature distribution and weld zone shape thickness which showed good agreement.

Influence of Blanching and Drying Air Temperature on Drying Kinetics of Banana Slices

Kumar Ravi,Pandey Om Prakash,Dhiman Sushil Kumar,Kumar Prashant 한국농업기계학회 2021 바이오시스템공학 Vol.46 No.4

Purpose Drying of agro products, analternative approach to truncate the post harvesting losses which is about 40%in case of banana as reported in literatures, is conducted for banana slicesusing tray dryer. The objective was to investigate the effect of blanching and dryingtemperature on drying kinetics of banana slices for which a comparative studyof the drying kinetics of the bananaslices under blanching and without blanching conditions was conducted. Methods The samples were made circularin shape with average diameter of 30mm and 2mm thickness. Drying was done atair velocity of 3ms-1 maintained at three different temperatures of60oC, 70oC and 80oC. Blanching of banana sliceswas done in an aqueous solution of citricacid for 1 minute. Results Comprison of blanching andwithout blancing samples was done based on drying kinetics, color, energy analysis, andcost analysis to optimize the drying conditions and reduce the process cost.Two thin layer drying models werefitted to the experimental data using nonlinear regression analysis and theresults were evaluated using statistical parameter. The significant effects ofdrying temperature, drying time and blanching on moisture content of bananaslices were analyzed by ANOVA (Analysis of Variance). Conclusions The blanchingtechnique was found as cost-effective dryingprocess as compared to the without blanching technique.

Cervicothoracic Thymic Cyst: An Unusual Presentation

Anjith Prakash Rajakumar,Jai Ganesh,Swaminathan Vaidyanathan,Ravi Agarwal 대한흉부외과학회 2018 Journal of Chest Surgery (J Chest Surg) Vol.51 No.2

Cervicothoracic thymic cysts are rare and difficult to diagnose preoperatively. We report a case of a cervicothoracic thymic cyst presenting as a lateral neck mass and mimicking a laryngocele in a 3-year-old boy and its definitive management.

Validation and Marker-Assisted Selection of Stem Rust Resistance Gene Sr2 in Indian Wheat Using Gel-Based and Gel-Free Methods

Gautam Vishwakarma,Ravi Prakash Sanyal,Abhijit Shitre,D. A. Gadekar,Ajay Saini,Bikram Kishore Das 한국작물학회 2019 Journal of crop science and biotechnology Vol.22 No.4

Stem rust resistance gene Sr2 is an important slow-rusting gene which has provided resistance against stem rust for many years. The Sr2 gene has durable resistance against all stem rust pathogens including the Ug99 group of races. It shows recessive inheritance and is linked with two phenotypic markers, Pseudo Black Chaff (PBC) and High Temperature-Induced Seedling Chlorosis (HTISC). However, direct screening as well as phenotypic marker-based screening for selection of Sr2 is difficult due to the effect of environmental factors and genetic background. Microsatellite marker Xgwm533 linked to Sr2 gene is useful for rapid screening of large populations. Here we report validation and use of Xgwm533 for screening 21 wheat lines and 24 wheat genotypes for the presence of the Sr2 gene. Furthermore, we also report the presence of a new, smaller allele (97 bp) of Xgwm533 locus in a few genotypes that was also confirmed by sequencing. We also demonstrate a new SYBR green dye, melt-curve/profile-based assay for convenient screening of the Xgwm533 locus, where the presence of different alleles can be differentiated in a gel-free manner.

Effect of AlN layer on the resistive switching properties of TiO2 based ReRAM memory devices

Bhawani Pratap Singh Rathore,Ravi Prakash,Davinder Kaur 한국물리학회 2018 Current Applied Physics Vol.18 No.1

The present study reports the resistive switching behaviour in Titanium Dioxide (TiO2) material, with possible implementations in non volatile memory device. The Cu/TiO2/Pt memory device exhibit uniform and stable bipolar resistive switching behaviour. The current-voltage (I-V) analysis shows two discrete resistance states, the High Resistance State (HRS) and the Low Resistance State (LRS). The effect of an additional AlN layer in the resistive memory cell is also investigated. The Cu/TiO2/AlN/Pt device shows a multilevel (tri-state) resistive switching. Multilevel switching is facilitated by ionic and metallic filament formation, and the nature of the formed filaments is confirmed by performing a resistance vs. temperature measurement. The bilayer device shows improved reliability over the single layer device. The formation of high thermal conductive interfacial oxy-nitride (AlON) layer is the main reasons for the enhancement of resistive switching properties in Cu/TiO2/AlN/Pt cell. The performance of device was measured in terms of endurance and retention, which exhibits good endurance over 105 cycles and long retention time of 105 s at 125 C. The above result suggests the feasibility of Cu/TiO2/AlN/Pt devices for multilevel non volatile ReRAM application.