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Ravikant Singh,Avik Samanta 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2
In this study, an attempt is made to examine the effects of loading pattern on critical temperature of the cold-formed steel (CFS) members under fire. Most of the past studies on CFS flexural members at elevated temperature included either point loading or uniform moment cases, however, critical temperature established for one loading pattern may prove to be unsafe or over-conservative in other loading scenario. Finite element model is developed using commercially available program ABAQUS and is validated against experimental and numerical results available in literature. Four types of loading patterns are considered namely, 4-point loading, 3-point loading, uniformly distributed load and uniform moment. Three load ratios: 0.3, 0.5 and 0.7 are considered in this study. Results from parametric study clearly indicate there is a significant effect on the critical temperature of the CFS steel flexural members due to change in loading patterns. Other parameters affecting the critical temperature such as non-dimensional slenderness, initial applied load levels, grade and geometric properties are also discussed in detail. Based on findings of this research two proposals are suggested in order to define critical temperature of the CFS flexural members under various loading conditions. Both the proposals are found to predict the safe critical temperature of CFS flexural members with accuracy.
Structural, thermal and conductive properties of Bi4-xMxV2O11 (M = La, Gd; 0 ≼ x ≼ 0.4) compounds
Deepti,Ravikant,M.L. Singla,K. Singh 한국물리학회 2009 Current Applied Physics Vol.9 No.6
Bi4-xMxV2O11 (M = La, Gd) was prepared by solid state reactions. The amount of La and Gd in the (Bi4-xMxV2O11) was varied in the range of (0 ≼ x ≼ 0.4). The addition of La and Gd to Bi4V2O11 electrolyte was found to stabilize the β crystalline phase for x ≼ 0.3. In addition, the phase transition corresponding β- to γ-phases are evident in the ionic conductivity plots as well as in XRD, DSC profiles of x ≽ 0.3 samples. The highest ionic conductivity was observed in Bi3.9La0.1V2O11 and Bi3.8Gd0.2V2O11 samples in the range of 10-3–10-4 S/cm for 700–500 ℃. These results were supported by impedance spectroscopy, Xray diffraction (XRD) and differential scanning calorimetry (DSC). Bi4-xMxV2O11 (M = La, Gd) was prepared by solid state reactions. The amount of La and Gd in the (Bi4-xMxV2O11) was varied in the range of (0 ≼ x ≼ 0.4). The addition of La and Gd to Bi4V2O11 electrolyte was found to stabilize the β crystalline phase for x ≼ 0.3. In addition, the phase transition corresponding β- to γ-phases are evident in the ionic conductivity plots as well as in XRD, DSC profiles of x ≽ 0.3 samples. The highest ionic conductivity was observed in Bi3.9La0.1V2O11 and Bi3.8Gd0.2V2O11 samples in the range of 10-3–10-4 S/cm for 700–500 ℃. These results were supported by impedance spectroscopy, Xray diffraction (XRD) and differential scanning calorimetry (DSC).
Anomalous Weak Ferromagnetism in Electron-doped Nd_(1−x)Sr_xMnO_3 (0.50 ≤ x ≤ 0.62) Thin Films
Pawan Kumar,Ravikant Prasad,Hari Krishna Singh,Rakesh Kumar Dwivedi,Avanish Kumar Srivastava,Mangala Prasad Singh 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4
In the present work we demonstrate that an anomalous weak ferromagnetism occurs in the composition range 0.50 ≤ x ≤ 0.62 in nanostructured thin films of Nd_(1−x)Sr_xMnO_3 (NSMO). Nanocrystalline thin films of overdoped manganite Nd_(1−x)Sr_xMnO_3 (<I>x</I> ∼ 0.50, 0.55, 0.60 and 0.62) on single crystal LaAlO_3 (001) substrates are grown by nebulized chemical spray pyrolysis technique. These single phase films possess average crystallite size ∼15 nm and the width of the grain boundaries is ∼1 - 2 nm. In the composition range 0.50 ≤ x ≤ 0.62, the ground state of NSMO is A-type antiferromagnetic (AFM) metallic. However, in the present films a broad paramagnetic (PM) to ferromagnetic (FM) transition is observed in all the compositions at T_C ∼ 226 K for x = 0.50 and 235 K for rest of the samples. All the films show a well-defined M-H hysteresis loop at 5 K. The coercivity (H_C) of these films is much larger than those having composition range 0.35 < x < 0.45. For x = 0.50 (0.62) film H_C = -1210 (-1484) Oe and +1162 (+1476) Oe. The asymmetry in coercivity suggests the presence of weak exchange bias effect in these films. It is observed that the FM ground state in these films have smaller magnetic moment per Mn atom than the expected full moment using the rigid model, we term this as a weak ferromagnetic (WFM) state arising due to the destabilization of the AFM ordering. We propose a possible scenario based on the combined effect of spin reorganization and enhanced orbital disordering in nanosized manganites, to explain the observed anomalous weak ferromagnetism in the A-type AFM spin ordered regime.
Akshay Jain,Ravikant Jain,Vivek Kiyawat 대한정형외과학회 2016 Clinics in Orthopedic Surgery Vol.8 No.3
Background: For surgical treatment of lumbar and lumbosacral tuberculosis, the anterior approach has been the most popular approach because it allows direct access to the infected tissue, thereby providing good decompression. However, anterior fixation is not strong, and graft failure and loss of correction are frequent complications. The posterior approach allows circumferential decompression of neural elements along with three-column fixation attained via pedicle screws by the same approach. The purpose of this study was to evaluate the outcome (functional, neurological, and radiological) in patients with lumbar and lumbosacral tuberculosis operated through the posterior approach. Methods: Twenty-eight patients were diagnosed with tuberculosis of the lumbar and lumbosacral region from August 2012 to August 2013. Of these, 13 patients had progressive neurological deterioration or increasing back pain despite conservative measures and underwent posterior decompression and pedicle screw fixation with posterolateral fusion. Antitubercular therapy was given till signs of radiological healing were evident (9 to 16 months). Functional outcome (visual analogue scale [VAS] score for back pain), neurological recovery (Frankel grading), and radiological improvement were evaluated preoperatively, immediately postoperatively and 3 months, 6 months, and 1 year postoperatively. Results: The mean VAS score for back pain improved from 7.89 (range, 9 to 7) preoperatively to 2.2 (range, 3 to 1) at 1-year followup. Frankel grading was grade B in 3, grade C in 7, and grade D in 3 patients preoperatively, which improved to grade D in 7 and grade E in 6 patients at the last follow-up. Radiological healing was evident in the form of reappearance of trabeculae formation, resolution of pus, fatty marrow replacement, and bony fusion in all patients. The mean correction of segmental kyphosis was 9.85° postoperatively. The mean loss of correction at final follow-up was 3.15°. Conclusions: Posterior decompression with instrumented fusion is a safe and effective approach for management of patients with lumbar and lumbosacral tuberculosis.
Nioshi Shah,Ravikant Kisana 이화여자대학교 한국여성연구원 2021 Asian Journal of Women's Studies(AJWS) Vol.27 No.2
In the absence of proper legislative regulation, women domestic workers in India are vulnerable not just to low wages but are subject to a host of unfair social practices and disrespectful behavior. This is because domestic work is part of deeper and ingrained casteist and patriarchal mores and practices. As such, these workers have to deal with many indignities as part of their employment. This paper attempts to highlight the daily humiliation and physical and mental costs experienced by women domestic workers. By documenting their lived realities at work and their oral narratives, we examine everyday tales of mistreatment, humiliation, mounting social anxiety, and escalating health issues. भारत में महिला गृहस्थ-मज़दूर के अधिकारोंकेलिए मज़बूत नियम-कानूनो कि गैर- मौजूदगी में, उन्हेरोज़मर्रा केकामकाजी जीवन में बहुत कुछ, जैसेअपर्याप्त वेतन और समाजिक निरादर, झेलना पड़ता है। यह इसलिए होता हैक्योंकि गृहस्थ-मजदूरोंके पेशे को जातिवाद और पितृसत्ता केआयामोंसेदेखा जाता है। हमारी शोध महिला गृहस्थ-मज़दूरो केमानसिक और शारीरिक तनावोंकी व्याख्या करती है। हमनेउनकी रोज़मर्रा की आपबीती का बयान लिया और पाया की उन्हें रोज़ सामाजिक निरदर्ता, अपमान और मानसिक एवं शारीरिक शिकायतोंसेजूझना पड़ता है।
Durability of fluoropolymer and antibacterial finishes on woven surgical gown fabrics
Vinay Kumar Midha,Ravikant Vashisht,Varsha Midha 한국의류학회 2014 Fashion and Textiles Vol.1 No.1
Commercially available polyester, polyester-cotton and cotton plain woven fabrics of 150 g/m2 weight and cotton woven fabric samples of 200 g/m2 weight with plain, twill and satin weave were studied for their suitability as surgical gowns. Water repellent and anti bacterial finishes were applied in single bath using pad-dry-cure method with four concentration levels of these finishes. Liquid barrier properties of samples were analyzed by water impact penetration and hydrostatic pressure test. Parallel streak method was used to measure the antibacterial activity on the fabric samples with Staphylococcus aureus. The fabric samples were also analyzed for air permeability and stiffness. Optimum concentration level of fluoropolymer and antibacterial finishes for achieving desired liquid barrier and antibacterial properties were determined for each fabric samples. Fabric samples were subjected to repeated laundering cycles to evaluate the durability of finishes. It was observed that polyester fabric samples and 200 g/m2 cotton twill woven fabrics show highest level of liquid barrier protection of Level 2 according to Association for the Advancement of Medical Instrumentation (AAMI) standards, with 4% and 7% fluoropolymers. The fabrics maintain their barrier protection upto 20 laundering cycles, whereas 100% cotton fabric samples show minimal liquid barrier protection and do not provide Level 2 protection even at 4% and 7% fluoropolymer.
Pawan Kumar,Rakesh Kumar Dwivedi,Pawan Kumar,Ravikant Prasad,Praveen Kumar Siwach,Hari Krishna Singh 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1
Thin films of La_(0.80)Sr_(0.20)Mn_(1−x)Cu_xO_3 with x = 0.00, 0.04, 0.08, 0.10, 0.15, and 0.20 were deposited on single-crystal LaAlO_3 (100) (LAO) substrates at 250 ± 10 ℃ by using a nebulized spray pyrolysis technique. Structural, surface, and transport characterizations were done by X-ray diffraction (XRD), atomic force microscopy (AFM) and the standard four probe technique, respectively. XRD patterns revealed the formation of single-phase polycrystalline films with a rhombohedral crystal structure. Cu substitution resulted in a uniform decrease in the metal insulator transition (T_(IM)) temperature up to x = 0.10, followed by a drastic decrease in T_(IM) for x = 0.15. Finally, the metal-insulator transition vanished for higher Cu concentrations (x = 0.20) in the observed temperature range. The variation in T_(IM) with the amount of added Cu is explained on the basis of the double exchange mechanism. Cu substitution has been found to perturb the Mn^(3+)-O-Mn^(4+) network and has a strong influence on T_(IM). The variation in resistivity maxima with temperature for different Cu concentrations showed a systematic trend up to x ∼ 0.10. We also explored the electrical conduction at T > T_(IM) in the framework of small polaron hopping in the adiabatic limit. The activation energy showed a strong dependence on the Cu concentration. The maximum magneto-resistance (MR) up to 10%, was observed for x = 0.15 at low temperatures.
Krishna Kumar Jaiswal,Ishita Banerjee,Swapnamoy Dutta,Ravikant Verma,Lokanadhan Gunti,Sharad Awasthi,Mayank Bhushan,Vinod Kumar,Mohamed Fahad Alajmi,Afzal Hussain 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-
The rapid emergence of multidrug-resistant microbes has turned into the main threat to public healthworldwide. The preparation and application of nanomaterial-based antimicrobials have increased toaddress this problem with great significance. This study has investigated the bio-fabrication of polycrystallineAg-NCs using BCE as a reducer and stabilizer under microwave irradiation. Ag-NCs formationswere optimized using varying concentrations of BCE and silver acetate. The XRD confirmed the incidenceof phases of nanostructured crystals of Ag/AgO/AgCl. The average crystallite sizes were calculated to be22.19, 36.65, and 36.65 nm for Ag, AgO, and AgCl, respectively. SERS spectra revealed the vibrationalmodes of the Ag and Ag-O stretch bands. FTIR spectra have indicated the incidence of chemical fingerprintsfor Ag-NCs and BCE biomolecules. SEM and HR-TEM micrographs exhibited the almost sphericalto the oval shape of 50 nm. SAED pattern attested to silver crystallinity in agreement with XRD analysis. The MIC values of the Ag-NCs against Escherichia coli, Staphylococcus aureus, Aspergillus brasiliensis, andRhizopus stolonifer were observed to be 120, 60, 200, and 100 mg/ml, respectively. This study has demonstratedthe facile method to prepare polycrystalline Ag-NCs with appropriate structural and morphologicalcharacteristics for antimicrobial applications.