Effect of Austempering Time on Electrochemical and Immersion Corrosion Behaviour of High Carbon, Carbide-Free Nanostructured Bainitic Steel in an Aqueous 3.5% NaCl

Sandeep Kumar Gupta,R. Manna,Kausik Chattopadhyay 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9

In the present study, carbide-free nanostructured bainite is produced by austempering high carbon and silicon steels at 250 °C. Fine pearlitic structure is also made by patenting the steels of selected compositions at 550 °C. The formation of carbidefreenanostructured bainite and retained austenite in the austempered steels and ferrite and cementite in patented steels wereconfirmed through X-ray diffraction and TEM studies. The optical, scanning and transmission electron microscopies revealthe presence of nanoscale bainite, filmy and blocky austenite in austempered steels and the presence of lamellar pearlite inpatented steels. Increasing austempering time enhances the amount of bainite but decreases the blocky retained austenite. Thecorrosion behaviour of the newly developed bainitic steels is compared with that of pearlitic steel of the same compositions. Electrochemical and immersion corrosion tests are conducted in an aqueous 3.5% NaCl solution. The corroded surfaces areanalyzed with the scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS). Corrosion resistanceincreases with increasing carbon percentage due to the formation of magnetite (Fe3O4), provided the content of other alloyingelements remains the same. The presence of Ni decreases corrosion rate significantly, i.e., enhances corrosion resistance,charge transfer resistance (Rct) and polarization resistance (Rp). Reducing retained austenite in nanostructured steel decreasesthe corrosion rate due to the lesser area of Galvanic couples and the formation of uniform, compact, and non-porous passivelayer. The bainitic steel samples demonstrated superior corrosion resistance to that of the pearlitic steel due to lesser cellformation. The corrosion mechanisms of high-carbon bainitic and pearlitic steel are discussed.

Optimization of InAlAs/InGaAs HEMT Performance for Microwave Frequency Applications and Reliability

Gupta, Ritesh,Aggarwal, Sandeep Kumar,Gupta, Mridula,Gupta, R.S. The Institute of Electronics and Information Engin 2004 Journal of semiconductor technology and science Vol.4 No.3

In the present paper efforts have been made to optimize InAlAs/InGaAs HEMT by enhancing the effective gate voltage ($(V_c-V_off)$) using pulsed doped structure from uniformly doped to delta doped for microwave frequency applications and reliability. The detailed design criteria to select the proper design parameters have also been discussed in detail to exclude parallel conduction without affecting the del ice performance. Then the optimized value of $V_c-V_off$and breakdown voltages corresponding to maximum value of transconductance has been obtained. These values are then used to predict the transconductance and cut-off frequency of the del ice for different channel depths and gate lengths.

Short Channel Analytical Model for High Electron Mobility Transistor to Obtain Higher Cut-Off Frequency Maintaining the Reliability of the Device

Gupta, Ritesh,Aggarwal, Sandeep Kumar,Gupta, Mridula,Gupta, R.S. The Institute of Electronics and Information Engin 2007 Journal of semiconductor technology and science Vol.7 No.2

A comprehensive short channel analytical model has been proposed for High Electron Mobility Transistor (HEMT) to obtain higher cut-off frequency maintaining the reliability of the device. The model has been proposed to consider generalized doping variation in the directions perpendicular to and along the channel. The effect of field plates and different gate-insulator geometry (T-gate, etc) have been considered by dividing the area between gate and the high band gap semiconductor into different regions along the channel having different insulator and metal combinations of different thicknesses and work function with the possibility that metal is in direct contact with the high band gap semiconductor. The variation obtained by gate-insulator geometry and field plates in the field and channel potential can be produced by varying doping concentration, metal work-function and gate-stack structures along the channel. The results so obtained for normal device structure have been compared with previous proposed model and numerical method (finite difference method) to prove the validity of the model.

A determination of occlusal plane comparing different levels of the tragus to form ala-tragal line or Camper’s line : a photographic study

Sandeep Kumar,Sandeep Garg,Seema Gupta 대한치과보철학회 2013 The Journal of Advanced Prosthodontics Vol.5 No.1

PURPOSE. The purpose of this study was to determine accurately the part of the tragus to be used to form the Ala-Tragal line or Camper’ line in orthognathic profile patients. MATERIALS AND METHODS. 150 dentate subjects with age of 18-40 years with orthognathic profile were sampled. Life-size lateral digital photographs of the face with fox plane were taken in natural head position. Different angles between Eye-Ear plane and occlusal plane (OT1-OP), Eye-Ear plane and ala-superior border of tragus (OT1-AT1), Eye-Ear plane and ala-middle border of tragus (OT1-AT2) and Eye-Ear plane and ala-inferior border of tragus (OT1-AT3) were calculated using computer software package, AutoCAD 2004. From the three angles formed by the Eye-ear plane (OT1 or FH plane) and the ala-tragal lines, the one closest to the angle formed between Eye-Ear plane (OT1) and occlusal plane (OP) was used to determine the occlusal plane of orientation. The obtained results were subjected to ANOVA F test, Tukey’ Honestly significant difference test, followed by Karl Pearson coefficient of correlation test. P values of less than 0.05 were taken as statistically significant. RESULTS. The mean of base line angle i.e. OT1-OP angle (11.96 ± 4.36) was found to be close to OT1-AT2 angle (13.67 ± 1.93) and OT1-AT3 angle (10.31 ± 2.03), but OT1-OP angle was found to be more closer to OT1-AT3 angle. Comparison of mean angles showed that OT1-OP angle in both males (11.68) and females (12.51) is close to OT1-AT3 angle (males- 11.01, females- 11.95). CONCLUSION. The line joining from ala to the lower border of the tragus was parallel to the occlusal plane in 53.3% of the subjects. There was no influence of the sex on the level of occlusal plane.

Optimization of InAlAs/InGaAs HEMT Performance for Microwave Frequency Applications and Reliability

Ritesh Gupta,Sandeep Kumar Aggarwal,Mridula Gupta,R.S.Gupta 대한전자공학회 2004 Journal of semiconductor technology and science Vol.4 No.3

In the present paper efforts have been made to optimize InALs/lnGaAs HEMT by enhancing the effective gate voltage (Vo-Voft) using pulsed doped structure from uniformly doped to delta doped for microwave frequency applications and reliability. The detailed design criteria to select the proper design parameters have also been discussed in detail to exclude parallel conduction without affecting the dewice performance. Then the optimized value of Vo-Voft and breakdown voltages corresponding to maximum value of transconductance has been obtained. These values are then used to predict the transconductance and cut-off frequency of the device for different channel depths and gate lengths.<br/> Index Terms-InAlAs/InGaAs heterostructure, delta doped, uniformly doped, pulsed doped, parallel conduction, channel confinement and breakdown, woltage<br/>

Tuning phase retardation behaviour of nematic liquid crystal using quantum dot

Swadesh Kumar Gupta,Dharmendra Pratap Singh,Rajiv Manohar,Sandeep Kumar 한국물리학회 2016 Current Applied Physics Vol.16 No.1

We here report on the phase retardation behavior of nematic liquid crystal (NLC) doped with CdSe quantum dot (QD). A study of birefringence and relative permittivity in 4-octyl-40-cyanobiphenyl (8CB) NLC and its variation with doping of QDs has been presented. The study shows improvement of NLC ordering after addition of QDs. The observed higher value of birefringence in QD doped NLC system has been attributed to improved alignment due to additional order in NLC by self assembled QDs. The improved order of NLC system has also been explained by a schematic illustration for pristine and QD doped NLC system. Study of relative permittivity has also revealed the ordering effect in QD dispersed NLC system.

Phylogeography and population expansion of Western Himalayan highly-erratically migratory painted lady butterfly (Lepidoptera: Nymphalidae: Vanessa cardui)

Singh Vinaya Kumar,Kumar Sanjay,Awasthi Sadhna,Gupta Sandeep Kumar 한국응용곤충학회 2021 Journal of Asia-Pacific Entomology Vol.24 No.4

Understanding population genetics, genetic diversity and the migration pattern of ecologically important species is crucial for effective conservation plans. We studied mitochondrial cytochrome c oxidase subunit-I (COI) gene variation in painted lady butterfly (Vanessa cardui) from different altitudinal gradients of Uttarakhand (Western Himalayas), India. We sequenced COI) gene of 91 samples and 22 COI sequences retrieved from GenBank as representatives of different localities for comparative analysis. We observed a total of 16 haplotypes, of which seven haplotypes were observed in Uttarakhand with intra-species sequence divergence ranges from 0.001 to 0.009. Haplotype (Hd) and nucleotide diversity (π) were comparatively low and averaging 0.635 and 0.002, respectively. The neutrality test, mismatch distribution graph and observed pattern of diversity indices (Hd and π) revealed population expansion. It was further confirmed by the Median Joining Network, which exhibited a star-like topology from the core haplotype, while the Bayesian phylogenetic tree displayed a mixing of haplo types from different localities to an identical clade. Haplotype organization in the Bayesian tree and Median Joining Network was not clustered as per their topographical affinity, indicating incomplete lineage sorting and late species population development or colonization in the novel area.

The effect of Valsalva maneuver in attenuating skin puncture pain during spinal anesthesia: a randomized controlled trial

Sanjay Kumar,Sujeet Kumar Singh Gautam,Devendra Gupta,Anil Agarwal,Sanjay Dhirraj,Sandeep Khuba 대한마취통증의학회 2016 Korean Journal of Anesthesiology Vol.69 No.1

Background: Valsalva maneuver reduces pain by activating sinoaortic baroreceptor reflex arc. We planned this study to evaluate the role of valsalva in attenuating spinal needle-puncture pain. Methods: Ninety American Society of Anesthesiologists (ASA) grade I and II enrolled patients undergoing elective surgery were randomized into 3 groups of 30 each. Group I (Control): didn’t blow; group II (Distraction): patients blew into rubber tube; Group III (Valsalva): blew into sphygmomanometer tube and raise mercury column up to 30 mmHg for at least 20 seconds. During above procedures, spinal puncture was performed with 25-gauge spinal needle. Results: Eighty-two patient data were analyzed. Incidence of spinal puncture pain was reduced to 10% (3 of 27) in Valsalva group as compared to 100% (28 of 28 in control group and 27 of 27 in Distraction group) observed in other two groups (P < 0.05). Severity of lumbar puncture pain as assessed by visual analog scale (0−10; where 0 is no pain and 10 is the worst imaginable pain) presented as Median (Interquartile range) were significantly reduced in the Valsalva group (0.0 [0.0] as compared to other 2 groups 2.0 [0.0] in the Distraction group and 3.0 [0.8] in Control group) (P < 0.05). Regarding time taken by CSF to fill spinal needle hub, there was no difference among the three groups (P > 0.05). None patient of all groups had post dural puncture headache (P > 0.05). Conclusions: Valsalva can be performed routinely in ASA I and II patients undergoing spinal anesthesia as it is safe, painless and non-pharmacological method of pain attenuation.

A Multicentre, Multinational, Open-Label, 52-Week Extension Study of Gemigliptin (LC15-0444) Monotherapy in Patients with Type 2 Diabetes Mellitus

양세정,민경완,Sandeep Kumar Gupta,박중열,Vyankatesh K. Shivane,Pankaj Kumar Agarwal,김두만,김용승,백세현 대한당뇨병학회 2021 Diabetes and Metabolism Journal Vol.45 No.4

The purpose of this extension study was to assess the long-term efficacy and safety of gemigliptin 50 mg in patients with type 2 diabetes mellitus (T2DM). Patients with T2DM who had completed the initial 24-week study comparing gemigliptin monotherapy with placebo were eligible to enrol. In the open-label, 28-week extension study, all enrolled patients received gemigliptin, regardless of the treatment received during the initial 24-week study period. The mean reduction±standard deviation (SD) in glycosylated hemoglobin (HbA1c) observed after 24 weeks of treatment (-0.6%±1.1%) was further decreased for the gemi-gemi group and the mean change in HbA1c at week 52 from baseline was -0.9%±1.2% (P<0.0001). For the pbo-gemi group, HbA1c decreased after they were switched to gemigliptin, and the mean change in HbA1c at week 52 from baseline was -0.7%±1.2% (P<0.0001). Furthermore, the overall incidence of adverse events demonstrated that gemigliptin was safe and well tolerated up to 52 weeks.

Rapid Prediction of Deflections in Multi-span Continuous Composite Bridges using Neural Networks

R. K. Gupta,Sushil Kumar,K. A. Patel,Sandeep Chaudhary,A.K. Nagpal 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4

This paper proposes closed form expressions for the rapid prediction of deflections in steel-concrete composite bridges of large number of spans subjected to service load. The proposed expressions take into account shear lag effect, flexibility of shear connectors and cracking in concrete slabs. Three separate neural networks have been developed for right exterior span, left exterior span and interior spans. The closed form expressions have been obtained from the neural networks developed in the study. The training, validating and testing data sets for the neural networks are generated using finite element software ABAQUS. The proposed expressions have been validated for number of bridges and the errors are found to be small for practical purposes. Sensitivity studies have been carried out using the proposed expressions to evaluate the suitability of input parameters. The use of the proposed expressions requires a computational effort that is fraction of that required for the finite element analysis, therefore, can be used for rapid prediction of deflection for everyday design.