G.A. Kumar

Kyushu Institute of Technology

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Richard E. Riman

Rutgers, The State University of New Jersey

John G. Brennan

Rutgers, The State University of New Jersey

Thomas J. Emge

Rutgers, The State University of New Jersey

Dhiraj K. Sardar

The University of Texas at San Antonio

M.G. Brik

University of Tartu

Madhab Pokhrel

The University of Texas Rio Grande Valley

N.V. Unnikrishnan

Mahatma Gandhi University

Anna Y. Kornienko

National Academy of Educational Sciences of Ukraine

Santhosh Chidangil

Manipal Academy of Higher Education

Mei Chee Tan

Singapore University of Technology and Design

Cooperative Institutions

Rutgers, The State University of New Jersey

The University of Texas at San Antonio

University of Electro-Communications

University of Minnesota

Cochin University of Science and Technology

Centro de Investigaciones en Optica

Rajendra Memorial Research Institute of Medical Sciences

Indian Council of Medical Research

University of Tartu

Periyar University

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Synthesis and spectroscopy of color tunable Y2O2S:Yb3+,Er3+ phosphors with intense emission

Journal of Alloys and Compounds (2011)

G.A. Kumar Madhab Pokhrel Anatolio Martínez Jiménez Robert Dennis I. L. Villegas

Photon Upconversion

Ytterbium

Emission intensity

Erbium

10.1016/j.jallcom.2011.11.006

Cite

Citations (106)

Lanthanide Clusters with Chalcogen Encapsulated Ln: NIR Emission from Nanoscale NdSe_x

Journal of the American Chemical Society (2010)

Brian F. Moore G.A. Kumar Mei Chee Tan Jesse Kohl Richard E. Riman

Ln(SePh)3 (Ln = Ce, Pr, Nd) reacts with elemental Se in the presence of Na ions to give (py)16Ln17NaSe18(SePh)16, a spherical cluster with a 1 nm diameter. All three rare-earth metals form isostructural products. The molecular structure contains a central Ln ion surrounded by eight five-coordinate Se2− that are then surrounded by a group of 16 Ln that define the cluster surface, with additional μ3 and μ5 Se2−, μ3 and μ4 SePh−, and pyridine donors saturating the vacant coordination sites of the surface Ln, and a Na ion coordinating to selenolates, a selenido, and pyridine ligands. NIR emission studies of the Nd compound reveal that this material has a 35% quantum efficiency, with four transitions from the excited state 4F3/2 ion to 4I9/2, 4I11/2, 4I13/2, and 4I15/2 states clearly evident. The presence of Na+ is key to the formation of these larger clusters, where reactions using identical concentrations of Nd(SePh)3 and Se with either Li or K led only to the isolation of (py)8Nd8Se6(SePh)12.

Chalcogen

10.1021/ja1069322

Cite

Citations (44)

Oxoclusters of the Lanthanides Begin to Resemble Solid-State Materials at Very Small Cluster Sizes: Structure and NIR Emission from Nd(III)

Journal of the American Chemical Society (2007)

Santanu Banerjee G.A. Kumar Richard E. Riman Thomas J. Emge John G. Brennan

The reaction of Nd(SePh)3 with SeO2 and Hg in pyridine gives the dodecanuclear cluster [(py)18Nd12O6Se4(Se2)4(SePh)4(Se2Ph)2Hg2(SePh)4][(Hg(SePh)3]2. In this compound the 12 Nd(III) ions are stacked in four sets of Nd3, with pairs of tetrahedral oxo ligands separating the Nd3 planes and Se, SeSe, SePh, pyridine, and HgSePh groups encapsulating the oxo core. Both the Nd−O bond lengths and the geometries about the oxo ions are remarkably similar to those found in solid-state Nd2O3. Near-IR emission experiments indicate that the cluster emission properties are less intense than those of highly emissive (DME)2Nd(SC6F5)3 or (THF)8Nd8O2Se2(SePh)16 but brighter than the nonemissive solid-state compound Nd2O3. Intensity variations are interpreted in terms of concentration quenching and phonon relaxation.

10.1021/ja069000a

Cite

Citations (46)

Spectral analysis of Er³⁺-, Er³⁺/Yb³⁺- and Er³⁺/Tm³⁺/Yb³⁺-doped TeO₂–ZnO–WO₃–TiO₂–Na₂O glasses

Journal of Physics Condensed Matter (2008)

G. Lakshminarayana Jianrong Qiu M.G. Brik G.A. Kumar I.V. Kityk

In this paper, we present the spectroscopic properties of Er(3+)-, Er(3+)/Yb(3+)- and Er(3+)/Tm(3+)/Yb(3+)-doped novel tellurite glasses. From the measured absorption spectra, Judd-Ofelt (JO) intensity parameters (Ω(2), Ω(4) and Ω(6)) have been evaluated for the Er(3+)-doped glass. With 980 nm excitation three strong upconversion emission bands centered at 505, 520 and 630 nm were observed for both Er(3+)- and Er(3+)/Yb(3+)-codoped glasses and the characteristic near-infrared emission bands were spectrally centered at 1.535 µm. The near-infrared spectra of Er(3+)- and Er(3+)/Yb(3+)-doped glasses have shown full width at half-maxima (FWHM) around 100 nm and 120 nm for the erbium [Formula: see text] transition, respectively. The measured maximum decay times of the [Formula: see text] transition (at wavelength 1.535 µm) are about 7.24 ms and 7.68 ms for 1.0Er(3+) and 1.0Er(3+)/ 2Yb(3+) (mol%)-codoped glasses, respectively. The maximum stimulated emission cross sections for the [Formula: see text] transition of Er(3+) and Er(3+)/Yb(3+) are 8.64 × 10(-21) and 6.78 × 10(-21) cm(2). From 1Er(3+)/ 1Tm(3+)/ 2Yb(3+) (mol%)-codoped glass, broad near-infrared emission bands centered at 1510 nm ([Formula: see text]) and 1637 nm ([Formula: see text]) with full width at half-maxima (FWHM) around 52 nm and 60 nm, respectively, were observed. These glasses with broad near-infrared emissions should have potential applications in tunable lasers and broadband optical amplification at low-loss telecommunication windows.

Photon Upconversion

Erbium

10.1088/0953-8984/20/37/375101

Cite

Citations (59)

CCDC 660405: Experimental Crystal Structure Determination

The Cambridge Structural Database (2007)

G.A. Kumar Richard E. Riman Lindsey Torres S. Banerjee M.D. Romanelli

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/ccq56dg

Cite

Citations (0)

Molecular Minerals™: Lyophillic Colloids for Ceramists

Journal of the American Ceramic Society (2006)

Richard E. Riman G.A. Kumar Santanu Banerjee John G. Brennan

This paper will focus on a novel class of inorganic compounds that we term as molecular minerals™ (MMs). MMs are clusters of ceramic fragments encapsulated with organic ligands. These compounds can be crystallized from solution as molecular single crystals and have well‐defined crystal structures that can be described with X‐ray diffraction methods. Most importantly, the ceramic clusters are perfectly monodisperse, and conventional synthetic techniques can be applied to facilitate control of size and composition. The organic encapsulate imparts solubility in organic solvents and polymers. More importantly, the solubility is thermodynamically driven to form a single‐phase system. Thus, unlike nanoparticles, the stability of clusters in solution is spontaneous rather than kinetically derived. A critical tool for creating MMs is a firm understanding of the fundamental issues governing cluster structure and stability. We have demonstrated a unique synthetic approach to these materials, capable of creating materials with oxo, sulfido, selenido, or tellurido ligands, whose ceramic fragment size can currently be varied from about 0.5 to 2 nm. Both homometallic and heterometallic lanthanide (Ln) complexes incorporating the group 12 metals Zn, Cd, and Hg have been prepared. Relative to prior work on metal organic or organometallic Ln complexes, MMs have unprecedented luminescent properties in terms of emission wavelength, emission intensity, and quantum efficiency. These materials match or exceed the luminescent properties of ceramics, glasses, and nanomaterials, while having the additional advantage of polymer solubility. Solubility facilitates the preparation of transparent molecular mineral nanocomposites that can be fabricated as bulk polymers, fibers, and films.

Dispersity

Nanomaterials

Hybrid material

10.1111/j.1551-2916.2006.01050.x

Cite

Citations (17)

Highly efficient upconversion luminescence in hexagonal NaYF4:Yb3+, Er3+ nanocrystals synthesized by a novel reverse microemulsion method

Optical Materials (2017)

M. Gunaseelan Sima Aminorroaya Yamini G.A. Kumar J. Senthilselvan

Microemulsion

Photon Upconversion

Nanorod

Hexagonal phase

10.1016/j.optmat.2017.10.012

Cite

Citations (51)

Efficient Water Flood Management Along with Novel Approach to Infill Drilling Resulting in Increased Oil Production at Lower Cost and Reduced GHG Intensity

Day 1 Mon, October 31, 2022 (2023)

G.A. Kumar Shaikhan Khadhuri Sameh Shehab Y. Hajri R. Yazidi

Abstract Water flood is dominant development mechanism to produce oil from lower Shuaiba carbonate reservoirs in North Oman. Efficient water flood management along with a novel approach to drill infill wells has resulted in increased oil production at lower GHG intensity while reducing cost and improving value. This paper describes steps that were taken to improve water utilization factor and sweep, in addition to measures adopted to reduce cost which resulted in significant value addition. Cluster wide effort to improve production from water flood fields in Cluster X focused on throughput and sweep improvement along with measures to reduce cost of drilling. Throughput improvement was mainly achieved through WRFM activities like stimulation and opening of closed in wells. Sweep improvement was achieved by increasing water injection in patterns with high injection efficiency. Digitalization workflows were used for better integration of production data with water flood management. Additionally, significant cost reduction and value improvement was realized through novel approach to infill drilling. Key to success was closing of high water cut wells before drilling new wells and side-tracking wherever possible. Throughput improvement achieved by enhanced WRFM practices resulted in the fields in cluster achieving highest throughput levels in the organization. This, along with sweep improvement resulted in stabilization of NFA decline, and higher start rates for new wells, which resulted in oil production gain of 2-5% which translates into more than a thousand barrels a day increase in oil production. Implementation of infill drilling approach mentioned earlier resulted in improved project economics due to the following:Several of new infill producers will be side-tracks instead of new wells. This can save between 20-40% of the well cost.The infill producers can re-use surface equipment and flow lines of closed in (high water cut) wells, resulting in substantial cost saving.The number of new injectors to be drilled can be significantly reduced, resulting in considerable cost saving. While not drilling these new injectors changes the sweep pattern, numerical simulation modelling has demonstrated that such impacts are small, and these additional injectors don’t pay for their cost. The approach described in this paper has been demonstrated in the cluster and has resulted in significant production gain and cost saving. Improvement in throughput and sweep not only results in higher production, but also reduces disposal water which is good for environment. Additionally, the approach to infill drilling, which is novel in the organization, results in reduction in GHG intensity and total emissions, apart from decrease in cost and improves value.

Infill

Produced water

10.2118/215955-ms

Cite

Citations (1)

A correlation study between meteorological parameters and COVID-19 pandemic in Mumbai, India

Diabetes & Metabolic Syndrome Clinical Research & Reviews (2020)

G.A. Kumar Ritu Raj Kumar

Rank correlation

Pandemic

Christian ministry

Dew point