We propose a hybrid precoding scheme for downlink multi-user multiple-input multiple-output (MU-MIMO) millimeter-wave (mmWave) systems. Firstly, the proposed precoder is designed by the beam steering ...condition and the zero-interference condition, which can be obtained with the information of angles of departure (AoDs) in frequency division duplex (FDD) systems. Then, the proposed precoder is decomposed into the radio frequency (RF) precoder and the baseband precoder without the loss of response. Also, array response vector selection algorithm is proposed to prevent the sum rate degradation in numerous users region. Simulation results show that the sum rate of the proposed hybrid precoder is higher than those of the block diagonalization (BD) based schemes in the region of more than 5 users and approaches the sum rate of the beam steering scheme without MU interference as the number of base station (BS) antennas increases.
Although miniaturized energy storage devices have emerging applications in portable and highly integrated electronic circuits, it is still challenging to develop fast and low-cost techniques to ...fabricate such micro-devices at an industrial scale. In this work, we report a novel, fast and environment-friendly photo-reduction technique to fabricate interdigitated graphene-based microelectrode patterns for in-plane microsupercapacitors (rG-O MSCs). Further selective electrodeposition of Co–Mn layered double hydroxide (CMLDH) on the interdigitated graphene microelectrodes is carried out for the fabrication of hybrid MSCs (HMSCs). The uniform deposition of three-dimensional vertical nanosheets of CMLDH provide more assessable active sites for electrolyte ions, which lead to a fast redox reaction, short ion diffusion length, and one-dimensional electron transport. The as-fabricated CMLDH HMSC exhibit high specific capacitance (36.38 mF cm−2) and energy density (6.82 μW h cm−2) at a current density of 0.71 mA cm−2 in 2 M KOH aqueous electrolyte. In addition, the CMLDH HMSC exhibit an excellent cycling stability up to 10,000 cycles. These findings pave the way for scalable low-cost fabrication of flexible high-performance MSCs.
•Photo-reduction technique was used for the first time to fabricate rG-O MSCs.•Selective electrodeposition of Co–Mn LDHs to fabricate HMSCs.•HMSCs exhibited high specific capacitance of 36.38 mF cm−2 and energy density of 6.82 μW h cm−2 at current density of 0.71 mA cm−2•HMSCs exhibited an excellent cycling stability up to 10,000 cycles.
The designing of novel materials is a fascinating and innovative pathway in materials science. Particularly, novel layered compounds have tremendous influence in various research fields. Advanced ...fundamental studies covering various aspects, including reactants and synthetic methods, are required to obtain novel layered materials with unique physical and chemical properties. Among the promising synthetic techniques, topochemical approaches have afforded the platform for widening the extent of novel 2D materials. Notably, the synthesis of binary layered materials is considered as a major scientific breakthrough after the synthesis of graphene as they exhibit a wide spectrum of material properties with varied potential applicability. In this review, a comprehensive overview of the progress in the development of metastable layered compounds is presented. The various metastable layered compounds synthesized from layered ternary bulk materials through topochemical approaches are listed, followed by the descriptions of their mechanisms, structural analyses, characterizations, and potential applications. Finally, an essential research direction concerning the synthesis of new materials is indicated, wherein the possible application of topochemical approaches in unprecedented areas is explored.
The increasing interest in novel materials requires in‐depth research on its mechanisms, structural analyses, characterization, and potential applications. The comprehensive progress of novel layered compounds synthesized via topochemical approaches is analyzed. Along with its current status from the existing literature, future research directions to address their challenges and unveil their potential are also discussed.
A practical route to the production of solution phase transferable graphene sheets using ionic liquid polymers (PIL) as a transferring medium is developed. Chemically converted graphene sheets ...decorated with PIL were found to be stable against the chemical reduction and well dispersed in the aqueous phase without any agglomeration. Upon the anion exchange of the PIL on graphene sheets, these PIL-modified graphene sheets in aqueous phase are readily transferred into the organic phase by changing their properties from hydrophilic to hydrophobic.
We report a case of occupational monkeypox virus infection from a needlestick injury in a healthcare worker in South Korea and review similar reports in the literature during 2022. Postexposure ...prophylactic treatment with a third-generation smallpox vaccine and antiviral agent tecovirimat inhibited local virus spread and alleviated lesion pain.
A graphene aerogel (GA) with a three-dimensional (3D) structure, ultra-lightweight nature, and high hydrophobicity was simply fabricated by the one-step pyrolysis of glucose and ammonium chloride. ...The as-synthesized GA exhibited a 3D interconnected microporous architecture with a high surface area of ∼2860 m2 g–1 and pore volume of 2.24 cm3 g–1. The hydrophobic GA (10 mg 100 mL–1) demonstrated rapid and excellent adsorption performance for the removal of food toxins such as various biogenic amines (histamine, cadaverine, and spermine) and the hazardous bacterium Staphylococcus aureus (a food contaminant and a cause of poor wound healing) from a liquid matrix with a maximum simultaneous adsorption capacity for multiple biogenic amines of >85.19% (histamine), 74.1% (cadaverine), and 70.11% (spermidine) and a 100% reduction in the viable cell count of S. aureus within 80 min of interaction. The outstanding adsorption capacity can be attributed to a highly interconnected porous network in the 3D architecture and a high surface-to-volume ratio. A case study using soy sauce spiked with multiple biogenic amines showed successful removal of toxins with excellent recyclability without any loss in absorption performance. Biocompatibility of the GA in terms of cell viability was observed even at high concentrations (83.46% and 75.28% at 25 and 50 mg mL–1, respectively). Confirmatory biocompatibility testing was conducted via live/dead cell evaluation, and the morphology of normal lung epithelial cells was examined via scanning electron microscopy showed no cellular shrinkage. Moreover, GA showed excellent removal of live colonies of S. aureus from the food matrix and immunoblotting analysis showed elevated protein expression levels of β-catenin and α-SMA (α-smooth muscle actin). The biocompatible sugar-based GA could simultaneously adsorb multiple biogenic amines and live bacteria and was easy to regenerate via simple separation due to its high floatability, hydrophobicity, surface area, and porosity without any structural and functional loss, making it especially relevant for food safety and biomedical applications.
Quantum beats, periodic oscillations arising from coherent superposition states, have enabled exploration of novel coherent phenomena. Originating from strong Coulomb interactions and reduced ...dielectric screening, two-dimensional transition metal dichalcogenides exhibit strongly bound excitons either in a single structure or hetero-counterpart; however, quantum coherence between excitons is barely known to date. Here we observe exciton quantum beats in atomically thin ReS2 and further modulate the intensity of the quantum beats signal. Surprisingly, linearly polarized excitons behave like a coherently coupled three-level system exhibiting quantum beats, even though they exhibit anisotropic exciton orientations and optical selection rules. Theoretical studies are also provided to clarify that the observed quantum beats originate from pure quantum coherence, not from classical interference. Furthermore, we modulate on/off quantum beats only by laser polarization. This work provides an ideal laboratory toward polarization-controlled exciton quantum beats in two-dimensional materials.
Electrochemical losses as a function of the micro-porous layer (MPL) arrangement in Proton Exchange Membrane Fuel Cells (PEMFCs) are investigated by electrochemical impedance spectroscopy (EIS). Net ...water flux across the polymer membrane in PEMFCs is investigated for various arrangements of the MPL, namely with MPL on the cathode side alone, with MPL on both the cathode and the anode sides and without MPL. EIS and water transport are recorded for various operating conditions, such as the relative humidity of the hydrogen inlet and current density, in a PEMFC fed by fully-saturated air. The cell with an MPL on the cathode side alone has better performance than two other types of cells. Furthermore, the cell with an MPL on only the cathode increases the water flux from cathode to anode as compared to the cells with MPLs on both electrodes and cells without MPL. Oxygen-mass-transport resistances of cells in the presence of an MPL on the cathode are lower than the values for the other two cells, which indicates that the molar concentration of oxygen at the reaction surface of the catalyst layer is higher. This suggests that the MPL forces the liquid water from the cathode side to the anode side and decreases the liquid saturation in GDL at high current densities. Consequently, the MPL helps in maintaining the water content in the polymer membrane and decreases the cathode charge transfer and oxygen-mass transport resistances in PEMFCs, even when the hydrogen inlet has a low relative humidity.
Various services and applications based on information and communications technology (ICT) are converging with cultural aspects of historical implementations. At the same time, developing a ...convergence course for non-ICT majors is becoming increasingly popular in universities. In this paper, we develop an AI application course for non-ICT major university students toward convergence with recommendation systems and Silk Road studies. Based on our five-year research on the martial arts, dance, and play of seven Silk Road countries, we have created and categorized an accessible database for 177 items in those countries. For our convergence course, we measure the similarity between the items for summary and perform collaborative filtering based on alternating least squares (ALS) matrix factorization so that our prototyped intelligent recommendation engine can predict the items in which a user might be interested. The course is designed to teach non-ICT major university students not only historical aspects of the Silk Road but also implementation aspects of recommendation systems with web services.
We report a template-free and easy solvent evaporation method during carbonizing a metal–organic framework (MOF) for the construction of large-scale meso- and macropore. While the direct thermal ...evaporation method of non-volatile solvent captured in micropore of a MOF is believed to reduce overall porosity of the resultant MOF, this method unprecedentedly directs the reorganization of MOFs toward the production of ultrahigh porous carbon materials. The obtained porous carbon materials possess a unique interconnected three-dimensional wormhole-like structure, high specific surface area (3000m2g−1), and exceptionally high pore volume (5.45cm3g−1). The micropores, along with accessible meso- and macropores, provide ion storage site and ion transport channel, respectively, that contributes to a rapid elimination of large amounts of salt within a very short period of time.
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