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( Sarada Ganguri ),진성호 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
A homoleptic and two new heteroleptic blue emitting Ir(III) complexes, tBu-FCNIr and tBuCN-FIracac/EtOCN-FIracac consisting of 2′,4″-difluorophenylpyridine (dfppy) with cyano (CN) group at 5′-position of the phenyl and tert-butyl (tBu) or ethoxy (EtO-) group at 4-position of the pyridine as main ligand are synthesized and characterized for phosphorescent organic light-emitting diodes (PhOLEDs). The tBuCN-FIracac and EtOCN-FIracac demonstrated high PLQYs of 90 ± 3% and 82 ± 3%, respectively, whereas tBu-FCNIr shows relatively low PLQY of 61 ± 3% measured in thin film. The emission spectra of EtOCN-FIracac, tBuCNFIracac and tBu-FCNIr represent substantial mixing of lower energy <sup>3</sup>MLCT and <sup>3</sup>LC excited states. The PhOLEDs based on tBuCN-FIracac and EtOCN-FIracac show one of the highest efficiencies ever achieved for blue color with a maximum EQE of 22.3% (39.2 cd A<sup>-1</sup>) and 21.5% (35.1 cd A<sup>-1</sup>), respectively with a simple device structure; while the similar device based on tBu-FCNIr display a maximum EQE of 16.2% (23.5 cd A<sup>-1</sup>).
Sarada, G.,Sim, B.,Moon, C.K.,Cho, W.,Kim, K.H.,Sree, V.G.,Park, E.,Kim, J.J.,Jin, S.H. Elsevier Science 2016 Organic Electronics Vol.39 No.-
We synthesized two new heteroleptic blue-emitting Ir(III) complexes tBuCN-FIrmMes and tBuCN-FIrdMes by using systematically tailored ancillary ligands 1-mesitylbutane-1,3-dione (mMes) and 1,3-dimesitylpropane-1,3-dione (dMes), respectively. Near-unity photoluminescence quantum yield (PLQY: 96 +/- 3%) was achieved for tBuCN-FIrmMes in doped films with short phosphorescence lifetime and high horizontal dipole ratio (Θ: 76%) than the di-mesityl complex, tBuCN-FIrdMes (PLQY: 75 +/- 3%, Θ: 71%). Here, introduction of mMes reduces the singlet-triplet splitting energy (ΔE<SUB>ST</SUB>), permanent dipole moment (μ), and the symmetry of tBuCN-FIrmMes as compared with tBuCN-FIrdMes, these parameters can highly affect the PLQY and Θ values. As a result, the blue phosphorescent organic light-emitting diode (PhOLED) of tBuCN-FIrmMes exhibits high external quantum efficiency (EQE) of ≥ 20% throughout a wide luminance range 1000-10000 cd/m<SUP>2</SUP> with a very low efficiency roll-off, which is crucial for solid-state lighting applications.
AN OPTIMAL NUMERICAL INTEGRATION METHOD OVER A LUNE BY USING AN EFFICIENT TRANSFORMATION TECHNIQUE
SARADA JAYAN,K. V. NAGARAJA 장전수학회 2016 Proceedings of the Jangjeon mathematical society Vol.19 No.3
In this paper, we derive an optimal numerical integration method to integrate functions over a lunar model, a closed region bounded by two different circular boundaries. The region is discretized into two and suitable efficient transformations are used to transform the regions to a zeroone square. After the transformation, a product formula is applied to derive the proposed numerical integration method. The generalized Gaussian quadrature nodes and weights for one dimension are used in the derived integration formula for evaluating the results. The results obtained for seven different functions are tabulated along with a comparative study in order to show that the proposed method gives more accurate results using less number of quadrature points and is the optimal one.
Sarada, Ganguri,Maheshwaran, Athithan,Cho, Woosum,Lee, Taegyun,Han, Si Hyun,Lee, Jun Yeob,Jin, Sung-Ho Elsevier 2018 Dyes and pigments Vol.150 No.-
<P><B>Abstract</B></P> <P>Pure blue phosphorescence with high quantum yield is crucial, yet highly challenging to achieve, for the successful application of phosphorescent organic light-emitting diodes (PhOLEDs) in display and lighting technologies. This study presents the design of three meridional tris-cyclometalated Ir(III) complexes (Ir1, Ir2 and Ir3) by introducing diphenylphosphine oxide (Ph<SUB>2</SUB>P = O) and/or fluorine (-F) group(s) on <I>N</I>-heterocyclic carbene (NHC) ligands (3-phenyl-3<I>H</I>-imidazo[4,5-<I>b</I>]pyridine or 1-phenyl-1<I>H</I>-imidazole) with the aim of achieving pure blue phosphorescence. Particularly, the introduction of –F on the NHC ligand greatly enhances the triplet (T<SUB>1</SUB>) energy and photoluminescence (PL) intensity of the Ir(III) complex (Ir3). Consequently, Ir3 exhibits ‘pure’ blue phosphorescence with high quantum yield (95%) and short triplet lifetimes (τ), the latter being beneficial for high radiative decay rates. Moreover, the Ir3 emitter shows pure blue Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.08), especially the ‘pure’ blue CIE <I>y</I> coordinate, in the PhOLEDs. However, Ir1 shows a maximum external quantum efficiency (EQE) of 8.6% at higher dopant concentration (20 wt%) with CIE coordinates of (0.16, 0.12).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three <I>N-</I>heterocyclic carbene based Ir(III) complexes were synthesized. </LI> <LI> Investigated the functionalization with diphenylphosphine oxide or fluorine. </LI> <LI> Achieved pure ‘blue’ coordinates (0.16, 0.08) for Ir3. </LI> <LI> The triplet energies of the phosphors are increased by the functionalization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Sarada Ganguri ),진성호 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
We designed and synthesized new blue emitting Ir(III) complexes, tBuCN-FIrmMes and tBuCN-FIrdMes, with the newly introduced ancillary ligands, 1-mesitylbutane-1,3-dione (mMes) and 1,3-dimesitylpropane-1,3-dione (dMes), respectively. The alteration of ancillary ligand with only one mesityl group resulted in excellent photophysical properties for tBuCN-FIrmMes such as the highest PLQY (96%), high Kr (8.73×10(5) s(-1)) and very low Knr (0.36×10(5) s(-1)) leading to the superior device performance compared with the PhOLEDs of tBuCN-FIrdMes. For instance, the PhOLED of tBuCN-FIrmMes showed EQEs of 22.4 % (max.) at 1000 cd m(-2), 19.8 % at 10 000 cd m(-2), and 16.5 % at 20 000 cd m(-2), that are higher compared with the PhOLED of tBuCN-FIrdMes; the EQEs are 17.8% (max.) at 1000 cd m(-2) and 14.9 % at 10 000 cd m(-2).
Dashtdar Masoud,Sarada K.,Hosseinimoghadam Seyed Mohammad Sadegh,Kalyan C. H. Naga Sai,Venkateswarlu A. N.,Goud B. Srikanth,Reddy C. H. Rami,Belkhier Youcef,Bajaj Mohit,Reddy B. Nagi 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.5
In the discussion of fault location due to the existence of multiple branches in the distribution network, diff erent locations are obtained and this shows the importance of detecting the faulted section in the distribution network . In this paper, the new idea of modulating the current and three-phase voltage of the line’s beginning and histogram analysis has been used for fault location in the power network. First, threephases of current and voltage of the line’s beginning are converted separately through convolution into a modulated current signal and a voltage signal, respectively. Then by dividing the density ratio of the modulated voltage by the modulated current, the distance to fault location can be estimated; but there is the possibility of obtaining several fault locations in the distribution network. In the following, the faulted section can be estimated through a histogram analysis of the modulated voltage. Simulation results show that by modulating the three-phase voltage, there is a possibility to eliminate the eff ects of fault resistance, fault occurrence angle, fault type on the algorithm’s accuracy. In the end, the suggested algorithm was implemented on a 735 kV transmission network and an IEEE-15bus distribution network whose results demonstrate the appropriate accuracy of the suggested algorithm.
Dynamic response of a laminated hybrid composite cantilever beam with multiple cracks & moving mass
Saritprava Sahoo,Sarada Prasad Parida,Pankaj Charan Jena 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.6
A novel laminated-hybrid-composite-beam (LHCB) of glass-epoxy infused with flyash and graphene is constructed for this study. The conventional mixture-rule and constitutive-relationship are modified to incorporate filler and lamina orientation. Eringen’s non-local-theory is used to include the filler effect. Hamilton’s principle based on fifth-order-layer-wiseshear- deformation-theory is applied to formulate the equation of motion. The analogous shear-spring-models for LHCB with multiple-cracks are employed in finite-element-analysis (FEA). Modal-experimentations are conducted (B&K-analyser) and the findings are compared with theoretical and FEA results. In terms of dimensionless relative-natural-frequencies (RNF), the dynamic-response in cantilevered support is investigated for various relative-crack-severities (RCSs) and relative-crackpositions (RCPs). The increase of RCS increases local-flexibility in LHCB thus reductions in RNFs are observed. RCP is found to play an important role, cracks present near the end-support cause an abrupt drop in RNFs. Further, multiple cracks are observed to enhance the nonlinearity of LHCB strength. Introduction of the first to third crack in an intact LHCB results drop of RNFs by 8%, 10%, and 11.5% correspondingly. Also, it is demonstrated that the RNF varies because of the lamina-orientation, and filler addition. For 0° lamina-orientation the RNF is maximum. Similarly, it is studied that the addition of graphene reduces weight and increases the stiffness of LHCB in contrast to the addition of flyash. Additionally, the response of LHCB to moving mass is accessed by appropriately modifying the numerical programs, and it is noted that the successive introduction of the first to ninth crack results in an approximately 40% to 120% increase in the dynamic-amplitude-ratio.