Parallel ADMM for robust quadratic optimal resource allocation problems

An alternating direction method of multipliers (ADMM) solver is described for optimal resource allocation problems with separable convex quadratic costs and constraints and linear coupling constraints. We describe a parallel implementation of the solver on a graphics processing unit (GPU) using a bespoke quartic function minimizer. An application to robust optimal energy management in hybrid electric vehicles is described, and the results of numerical simulations comparing the computation times of the parallel GPU implementation with those of an equivalent serial implementation are presented

Understanding the electrochemical performance of LiNi0. 5Mn1.5O4 coated with Yttria and distributed over graphene nanosheets as cathode in li-ion batteries

LiNi0.5Mn1.5O4 is a promising cathode material for lithium-ion batteries with a high-voltage spinel structure. A microwave-assisted chemical co-precipitation method was used to synthesize Y2O3 coated quasi-spheres of LiNi0.5Mn1.5O4. The coating of Y2O3 and subsequent wrapping of quasi-spheres in graphene nanosheets does not alter the volume or promote the formation of unwanted phases. TGA analysis shows high thermal stability in the material. The material has an initial capacity of 133 mAh g−1 at C/10 with a retention of 98% after 100 cycles. In addition, cathode samples show a good capacity of 132 g−1 after 20 cycles at higher temperatures (55 °C). Oxide coatings protect the particles from ionic leaching but limit the electrical conductivity of the materials. However, graphene enhances the conductivity of the synthesized material and wraps active particles in a conductive channel. Due to the synergistic design of the material and the robust manufacturing technique, parasitic reactions are suppressed without affecting the electrical conductivity. To increase their cyclic performance, the suggested material synthesis approach may successfully be applied to various electrode materials

Influence of graphene wrapped-cerium oxide coating on spherical LiNi0.5Mn1.5O4 particles as cathode in high-voltage lithium-ion batteries

Cobalt-free LiNi0.5Mn1.5O4 (Lithium Nickel Manganese Oxide; LNMO) has garnered considerable interest as a cathode material due to its high working voltage, lower cost, and environmental friendliness. However, LNMO cathodes currently exhibit low cyclability and capacity deterioration, severely restricting their use on a broader scale. To this end, microwave-assisted chemical co-precipitation was used to produce spherical aggregated nanoparticles of LiNi0.5Mn1.5O4 (LNMO) coated with CeO2 (LNMO-Ce) and wrapped in graphene (LNMO-Ce-GO). Structural analysis demonstrates that the ceria coating along with the graphene wrapping prevents unwanted phases from forming and altering the morphology of the LNMO microspheres. LNMO-Ce-GO exhibits a discharge capacity of 132.4 mAhg−1 at the C/10 rate with a capacity retention of 95.3 % after 100 cycles, compared to LNMO-Ce and bare LNMO samples that provide a capacity retention of 91.6 % and 84.7 % respectively. DSC analysis elucidate that the ceria coating helps to suppress the adverse reactions at the electrode/electrolyte interface and reduce the Mn3+ dissolution due to the Jahn Teller effect, increasing cell cyclability. The graphene wrapping reduces material aggregation and provides conductive pathways that significantly improve the electrochemical performance of the LNMO cathode. This innovative material design strategy can be efficiently expanded to other classes of lithium-ion battery cathode materials to enhance their electrochemical performance.This publication was supported by the Qatar National Research Fund's NPRP Grant # NPRP11S-1225-170128 (a member of the Qatar Foundation). This publication also sponsored via an internal grant from Qatar University (QUCG-CENG-20/21-2). Open Access funding provided by the Qatar National Library. The writers are entirely responsible for the statements stated herein. Moreover, the authors would like to express gratitude to the Central Laboratory Unit (CLU) at Qatar University, for conducting microstructural investigations (FE-SEM/EDX and HR-TEM). The authors would also like to thank Jeffin James Abraham for his technical assistance with various electrochemical characterizations.Scopu

INFLUENCE OF METAL OXIDE COATINGS ON THE PERFORMANCE OF HIGH-VOLTAGE LiNi0.5Mn1.5O4 (LNMO) CATHODE MATERIALS FOR RECHARGEABLE LITHIUM-ION BATTERIES (LIBS)

Lithium-ion batteries (LIBs) have been publicized as suitable candidates for their utilization in portable electronics and electric vehicles (EVs). This move has been made in the past decade to address global warming and climate change concerns. The cathode materials utilized in the rechargeable lithium-ion batteries are vital as they primarily donate lithium-ions in the system. Spinel LiNi0.5Mn1.5O4 (Lithium Nickel Manganese Oxide; LNMO) has attracted much attention as a cathode material due to its high voltage of 4.7 V vs. Li, high specific energy of 700 Wh/kg, lower cost, and environmental friendliness. However, LNMO cathodes are currently suffering from poor cyclability and capacity degradation, hindering commercialization. Many strategies have been suggested in the literature to address the challenges associated with spinel cathode materials. Among those, surface modification techniques like surface coatings have proven to be promising and may enhance the electrochemical performance of LNMO. Towards this direction, during the proposed research work, LNMO will be synthesized by microwave-assisted chemical co-precipitation technique and then coated with graphene wrapped ceramic materials (Al2O3 and CeO2). A comparison of structural, thermal, and electrochemical performance of pristine material with the coated LNMO will be accomplished. The novelty of the proposed research work resides in the fact that synthesis of LNMO by the proposed method and its surface modification through graphene wrapped ceramic materials has not yet been reported

Carbon dots as versatile nanomaterials in sensing and imaging: Efficiency and beyond

Carbon dots (CDs) have emerged as a versatile and promising carbon-based nanomaterial with exceptional optical properties, including tunable emission wavelengths, high quantum yield, and photostability. CDs are appropriate for various applications with many benefits, such as biocompatibility, low toxicity, and simplicity of surface modification. Thanks to their tunable optical properties and great sensitivity, CDs have been used in sensing as fluorescent probes for detecting pH, heavy metal ions, and other analytes. In addition, CDs have demonstrated potential as luminescence converters for white organic light-emitting diodes and light emitters in optoelectronic devices due to their superior optical qualities and exciton-independent emission. CDs have been used for drug administration and bioimaging in the biomedical field due to their biocompatibility, low cytotoxicity, and ease of functionalization. Additionally, due to their stability, efficient charge separation, and low recombination rate, CDs have shown interesting uses in energy systems, such as photocatalysis and energy conversion. This article highlights the growing possibilities and potential of CDs as adaptable nanomaterials in a variety of interdisciplinary areas related to sensing and imaging, at the same time addressing the major challenges involved in the current research and proposing scientific solutions to apply CDs in the development of a super smart society

Impact of coatings on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials: A focused review

The application of Lithium-ion batteries (LIBs) in portable electronics and electric vehicles (EVs) has increased in the past decade. Extended commercialization of LIBs for advanced applications requires the development of high-performance electrode materials. LiNi0.5Mn1.5O4 (Lithium Nickel Manganese Oxide referred to as LNMO) has attracted much attention as a cathode material due to its high voltage and energy density, lower cost, and environmental friendliness. However, LNMO cathodes are currently suffering from poor cyclability and capacity degradation at elevated temperatures. Many strategies have been suggested in the literature to address the challenges associated with numerous families of cathode materials. Among those, surface modification techniques like surface coatings have proven to be promising. Surface coatings have a good effect on the electrochemical performance of LNMO, as these result in increasing electronic and ionic conductivity, fast ions mobility and high diffusivity. Towards this direction, a systematic review of research progress carried out in the area of coated LNMO has been summarized. More precisely, the impact of numerous coating materials in improving cyclability and capacity retention at elevated temperatures of LNMO has been discussed along with a variety of coating synthesis technologies.This work was supported by NPRP Grant # NPRP11S-1225-170128 from Qatar National Research Fund (a member of the Qatar Foundation ). This work was also made possible by the Qatar University Internal Grant ( QUCG-CENG-20/21-2 ). Statements made herein are solely the responsibility of the authors.Scopu

Virtual Occlusions Through Implicit Depth

For augmented reality (AR), it is important that virtual assets appear to `sit among' real world objects. The virtual element should variously occlude and be occluded by real matter, based on a plausible depth ordering. This occlusion should be consistent over time as the viewer's camera moves. Unfortunately, small mistakes in the estimated scene depth can ruin the downstream occlusion mask, and thereby the AR illusion. Especially in real-time settings, depths inferred near boundaries or across time can be inconsistent. In this paper, we challenge the need for depth-regression as an intermediate step. We instead propose an implicit model for depth and use that to predict the occlusion mask directly. The inputs to our network are one or more color images, plus the known depths of any virtual geometry. We show how our occlusion predictions are more accurate and more temporally stable than predictions derived from traditional depth-estimation models. We obtain state-of-the-art occlusion results on the challenging ScanNetv2 dataset and superior qualitative results on real scenes.Comment: Accepted to CVPR 202

LiMn2O4 – MXene nanocomposite cathode for high-performance lithium-ion batteries

Lithium-ion batteries still face many significant challenges for practical applications, including low discharge capacity, cyclic efficiency, initial coulombic efficiency, areal performance, volumetric capacity, and high materials cost. LiMn2O4 (LMO) characterized by its spinel structure, is a highly appealing cathode material attributed to its remarkable energy density, cost-effectiveness, and minimal environmental impact. However, LMO experiences capacity fading while shifting between the C rates. The 2D material MXene with its very high electrical conductivity functions as a conductive matrix, allowing for volume expansion and contraction during Li+ intercalation while retaining structural and electrical connections. In this work, the LiMn2O4-MXene (LMO-MX) nanocomposite was synthesized by a cost-effective microwave-assisted chemical coprecipitation and examined. Structural characterization confirmed the effective synthesis of LMO-MX nanocomposite. Electrochemical characterizations demonstrate that LMO-MX nanocomposites exhibit outstanding electrochemical performance, with an initial specific discharge capacity of roughly 111 mAhg-1 at 0.1 C, and capacity retention of 95.2% after 100 cycles in contrast to the pristine LMO which gave an initial specific discharge capacity of 97 mAhg-1 and cyclability of 89.3%. The incorporation of MXenes enhances the electrochemical characteristics of LMO cathode material and implies that MXene-based nanocomposites might be useful as cathodes in high-performance lithium-ion batteries.Other Information Published in: Energy Reports License: http://creativecommons.org/licenses/by/4.0/See article on publisher's website: https://dx.doi.org/10.1016/j.egyr.2024.02.006</p