http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
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.