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Kirdsiri, K.,Raja Ramakrishna, R.,Damdee, B.,Kim, H.J.,Kaewjaeng, S.,Kothan, S.,Kaewkhao, J. Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.749 No.-
<P><B>Abstract</B></P> <P>The glass composition of 50Li<SUB>2</SUB>O-20MO-29.7B<SUB>2</SUB>O<SUB>3</SUB>-0.3Sm<SUB>2</SUB>O<SUB>3</SUB> (M = Mg/Ca/Sr/Ba), has been synthesized by the conventional melt quench technique. Density measurements were studied and shows large for LBaBSm glass sample (2.9049 g/cm<SUP>3</SUP>) than any other alkali species (Mg/Ca/Sr). Variation in density is due to the ionic radii of the alkali ion species (M = Mg/Ca/Sr/Ba). Optical absorption spectra of Sm<SUP>3+</SUP> doped LMgB, LCaB, LSrB and LBaB glass systems were studied and shows very intense peaks at NIR region. The emission and excitation spectra of these glasses were studied and emission spectra shows green, yellow and reddish - orange emission bands at 563, 600, 646 and 706 nm. Judd–Ofelt (JO) intensity analysis had been performed and JO parameters were estimated for 0.3 mol.% Sm<SUB>2</SUB>O<SUB>3</SUB> doped 50Li<SUB>2</SUB>O-20MO-29.7B<SUB>2</SUB>O<SUB>3</SUB> (M = Mg/Ca/Sr/Ba) glasses. Radiative properties such as transition probabilities, stimulated emission cross-sections and branching ratios were estimated by using JO parameters and luminescence spectra. The decay curves of these glasses exhibit single exponential nature. The CCT values obtained from CIE for these glass samples shows 1663 K for indicating orange emission under 403 nm excitation wavelength.</P> <P><B>Highlights</B></P> <P> <UL> <LI> J-O parameters of Li2O-MO-B2O3 (M = Mg/Ca/Sr/Ba) glass doped Sm<SUP>3+</SUP> studied. </LI> <LI> LBaBSm0.3 glass show more asymmetry around Sm<SUP>3+</SUP> ion than other transition ions. </LI> <LI> LBaBSm0.3 glass emit bright reddish-orange luminescence at 403 nm excitation. </LI> <LI> The CCT values obtained for glass samples around 1663 K in orange emission. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>UV–Vis–NIR spectra of LMOBSm0.3 (M = Mg, Ca, Sr, Ba) samples.</P> <P>[DISPLAY OMISSION]</P>
Manjunath, B.S.,Ramakrishna, D.S. Techno-Press 2009 Interaction and multiscale mechanics Vol.2 No.2
Machine or structural members subjected to fatigue loading will have a crack initiated during early part of their life. Therefore analysis of members with cracks and other discontinuities is very important. Finite element method has enjoyed widespread use in engineering, but it is not convenient for crack problems as the region very close to crack tip is to be discretized with very fine mesh. However, as the body force method (BFM), requires only the boundary of the discontinuity (crack or hole) to be discretized it is easy versatile technique to analyze such problems. In the present work fundamental solution for concentrated load x + iy acting in the semi-infinite plate at an arbitrary point $z_0=x_0+iy_0$ is considered. These fundamental solutions are in complex form ${\phi}(z)$ and ${\psi}(z)$ (England 1971). These potentials are known as Melan potentials (Ramakrishna 1994). A crack in the semi-infinite plate as shown in Fig. 1 is considered. This crack is divided into number of divisions. By applying pair of body forces on a division, the resultant forces on the remaining 'N'divisions are to be found for which ${\phi}_1(z)$ and ${\psi}_1(z)$ are derived. Body force method is applied to calculate stress intensity factor for crack in semi-infinite plate. Also for the case of crack emanating from circular hole in semi-infinite plate radial stress, hoop stress and shear stress are calculated around the hole and crack. Convergent results are obtained by body force method. These results are compared with FEM results.
Vasculosyncytial membrane in relation to syncytial knots complicates the placenta in preeclampsia
K. Devi Sankar,P. Sharmila Bhanu,Sujatha Kiran,B. A. Ramakrishna,V. Shanthi 대한해부학회 2012 Anatomy & Cell Biology Vol.45 No.2
The vasculosyncytial membrane (VSM), primary site of fetomaternal exchange is formed when syncytiotrophoblast surrounds the terminal villi and make a close contact with capillaries. Some syncytiotrophoblast forms thin single layer of villous and some syncytial nuclei become piled up to form the syncytial knots (SKs). Undoubtedly there is a clear-cut inverse relation between villous VSM and fetal hypoxia. In preeclampsia (PE) the hypoxia injury disrupts the syncytial architecture which in turn initiates other complications of PE. Present study was designed to observe the morphological and histomorphometric features of 84 placentas from control and PE (42 each) collected from Department of Obstetrics and Gynecology. Neonatal weight and placental weight were reduced in PE than the controls but the feto-placental index did not differ. The SK density and VSM thickness was found to be increased and was statistically significant in PE cases. In relation to SKs, the VSM thickness was twofold increased than the controls and was statistically significant. The SKs in the present study were classified as type-1, 2a, 2b, and 3. Type 1 was found to be 62% in control and 47% in PE, type 2a and 2b were 38% in control and 37% in PE, and type 3 was in 8% of PE cases. All the parameters of present study reveal the adverse effects of PE influencing on both morphological and microscopical features of the placenta resulting in fetal hypoxia.
Design and stress analysis of femur bone implant with composite plates
Ramakrishna, S.,Pavani, B. Techno-Press 2020 Biomaterials and Biomechanics in Bioengineering Vol.5 No.1
Development of lightweight implant plates are important to reduce the stress shielding effect for a prosthesis of femur bone fractures. Stainless steel (SS-316L) is a widely used material for making implants. Stress shielding effect and other issues arise due to the difference in mechanical properties of stainless steel when compared with bone. To overcome these issues, composite materials seem to be a better alternative solution. The comparison is made between two biocompatible composite materials, namely Ti-hydroxyapatite and Ti-polypropylene. "Titanium (Ti)" is fiber material while "hydroxyapatite" and "polypropylene" are matrix materials. These two composites have Young's modulus closer to the bone than stainless steel. Besides the variety of bones, present paper constrained to femur bone analysis only. Being heaviest and longest, the femur is the most likely to fail among all bone failures in human. Modelling of the femur bone, screws, implant and assembly was carried out using CATIA and static analysis was carried out using ANSYS. The femur bone assembly was analyzed for forces during daily activities. Ti-hydroxyapatite and Ti-polypropylene composite implants induced more stress in composite implant plate, results less stress induced in bone leading to a reduction in shielding effect than stainless steel implant plate thus ensuring safety and quick healing for the patient.
( S. Ramakrishna ),( B. Surendra Nath ),( Jayaprakash ) 한국잠사학회 2007 International Journal of Industrial Entomology Vol.8 No.2
A detailed evaluation of relative toxicity of fluoride to the 5th instar larvae of PM and NB4D2 races of silkworm and the effects of lethal, sublethal and prevailing levels of fluoride in groundwater on the growth, economic characters and fecundity of the silkworm, Bombyx mori (Lepidoptera: Bombycidae) were studied. The feeding of mulberry, Morus alba leaves treated with lethal and sublethal doses of fluoride to PM and NB4D2 races of silkworms from the beginning of the 5th instar to the end of the feeding period resulted in significant reduction in growth, single cocoon weight, single shell weight, silk index, average filament length, and fecundity when compared to controls. These changes were more pronounced on exposure to lethal dose than sublethal dose and in general, the changes induced by fluoride were more striking in NB4D2 than PM, indicating the greater resistance of PM to higher fluoride levels. Groundwater quality in sericulturally important villages of Karnataka and Andhra Pradesh States has been studied with special reference to the presence of fluoride. On exposure to dose of prevailing levels in the waters of sericulturally important areas, die changes observed on growth, economic characters and fecundity were slightly lower when compared to controls and the decrease was found to be insignificant (P≥0.05). It was concluded that, though minute dose (4.0 ppm) of fluoride did not have any toxic impact, it is toxic at higher concentrations to silkworms.
S. Ramakrishna,B. Surendra Nath,Jayaprakash 한국잠사학회 2004 International Journal of Industrial Entomology Vol.8 No.2
A detailed evaluation of relative toxicity of fluoride to the 5th instar larvae of PM and NB4D2 races of silkworm and the effects of lethal, sublethal and prevailing levels of fluoride in groundwater on the growth, economic characters and fecundity of the silkworm, Bombyx mori (Lepidoptera: Bombycidae) were studied. The feeding of mulberry, Morus alba leaves treated with lethal and sublethal doses of fluoride to PM and NB4D2 races of silkworms from the beginning of the 5th instar to the end of the feeding period resulted in significant reduction in growth, single cocoon weight, single shell weight, silk index, average filament length, and fecundity when compared to controls. These changes were more pronounced on exposure to lethal dose than sublethal dose and in general, the changes induced by fluoride were more striking in NB4D2 than PM, indicating the greater resistance of PM to higher fluoride levels. Groundwater quality in sericulturally important villages of Karnataka and Andhra Pradesh States has been studied with special reference to the presence of fluoride. On exposure to dose of prevailing levels in the waters of sericulturally important areas, the changes observed on growth, economic characters and fecundity were slightly lower when compared to controls and the decrease was found to be insignificant (P ³ 0.05). It was concluded that, though minute dose (4.0 ppm) of fluoride did not have any toxic impact, it is toxic at higher concentrations to silkworms.