Fully Distributed Multicast Routing Protocol for IEEE 802.15.8 Peer-Aware Communication

The IEEE 802.15.8 provides peer-aware communication (PAC) protocol for peer-to-peer infrastructureless service with fully distributed coordination. One of the most promising services in IEEE 802.15.8 is group multicast communication with simultaneous membership in multiple groups, typically up to 10 groups, in a dense network topology. Most of the existing multicast techniques in mobile ad hoc networks (MANET) have significant overhead for managing the multicast group and thus cannot be used for fully distributed PAC networks. In this paper, we propose a light-weight multicast routing protocol referred to as a fully distributed multicast routing protocol (FDMRP). The FDMRP minimizes routing table entries and thus reduces control message overhead for its multicast group management. To balance the control message, all nodes in the network have a similar number of routing entries to manage nodes in the same multicast group. To measure the effectiveness of the proposed FDMRP against the existing schemes, we evaluated performance by OPNET simulator. Performance evaluation shows that the FDMRP can reduce the number of routing entries and control message overhead by up to 85% and 95%, respectively, when the number of nodes is more than 500

Highly Enhanced Raman Scattering on Carbonized Polymer Films

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10(-8) M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors

Antibody Detection in Healthcare Workers after Vaccination with Two Doses of the BNT162b2 or ChAdOx1 Vaccine

Background: Due to the COVID-19 pandemic, from 2020, many pharmaceutical companies have developed vaccines. To determine the efficacy of AstraZeneca’s and Pfizer’s vaccines, which were the first and second vaccines to be approved in Korea, respectively, we developed a method to measure their antibody-generating efficacies using immunology analyzers and a rapid antibody test available in Korea. Methods: The antibody-stimulating efficacies of the Pfizer and AstraZeneca vaccines were evaluated using Centaur. XPT SARS-CoV-2 (Siemens Healthineers, Germany), Elecsys. Anti-SARS-CoV-2 S (Roche Diagnostics, Germany), and STANDARD F SARS-CoV-2 nAb FIA (SD Biosensor, Korea). Healthcare workers were enrolled in two groups: the Pfizer (121) and AstraZeneca (117) groups. Antibody levels were measured pre-vaccination, three weeks after vaccination, and 16 weeks after vaccination. Results: The Pfizer group comprised 41 males and 80 females, while the AstraZeneca group comprised 38 males and 79 females. Antibody results were analyzed after excluding four individuals who had recovered from COVID-19. Between weeks 3 and 16, there was no significant difference (P= 0.5, 1.0) between the results of the Roche and Siemens antibody tests in the Pfizer vaccine group. However, the SD biosensor results comparing with the Roche and Siemens antibody tests at three weeks after the initial vaccination showed a significant difference (P < 0.0001). Analysis of the Roche antibody test results before, at three weeks, and at 16 weeks after the administration of the Pfizer and AstraZeneca vaccines revealed a statistically significant difference between before and at three weeks after the first injection (P < 0.0001). After two doses of the Pfizer and AstraZeneca vaccines, antibody formation was above the 90th percentile of the measurement range in all subjects

Realizing battery-like energy density with asymmetric supercapacitors achieved by using highly conductive three-dimensional graphene current collectors

We report a three-dimensional graphene network decorated with nickel nanoparticles as a current collector to achieve outstanding performance in Ni(OH)(2)-based supercapacitors with excellent energy density. A cost-efficient and single-step fabrication method creates nickel-particle decorated three-dimensional graphene networks (Ni-GNs) with an excellent electrical conductivity of 107 S m(-1) and a surface area of 16.4 m(2) g(-1) that are superior to those of carbon alternatives and commercial 3D-Ni foam, respectively. The supercapacitor in which Ni(OH)(2) active materials are deposited on Ni-GNs exhibited an outstanding capacitance value of 3179 F g(-1) at 10 A g(-1) in a three-electrode system and 90% of capacitance retention after 10 000 cycles. Furthermore, it showed an outstanding energy density of 197.5 W h kg(-1) at a power density of 815.5 W kg(-1) when tested in a two-electrode system. To the best of our knowledge, our device realized the world record value of energy density with a high rate capability and good cycle stability among Ni(OH) 2-based supercapacitors. The excellent electrical properties of easily synthesized Ni-GNs as the ideal current collector clearly suggest a straightforward way to achieve great performance supercapacitors with both high energy density and power density

Stacking-Free Porous Graphene Network for High Capacitive Performance

Reduced graphene oxide (rGO) composites for energy-related applications have attracted increasing attention. However, previous studies on rGOs still showed limitations because of unresolved several issues including p-p stacking between the graphene sheets, low wettability, and relatively high electrical resistance. Here, we report a fabrication method for a stacking-free porous graphene network (PGN) based on the intercalation of oxidized multiwall carbon nanotubes and graphitic carbon nitrides into partially exfoliated GO sheets with covalent sulfate bonding between each layer, followed by hydrothermal reduction to rGO. The three-dimensional PGN with high wettability and low electrical resistance provided a high capacitance of 338 F/g at 1 A/g, an outstanding energy density of 36.0 W h/kg at a power density of 1496.1 W/kg, and nearly 100% capacitance retention after 10,000 cycles. Our strategy overcomes the previous limitations of rGO and presents remarkable potential of 3D stacking-free rGO composites for practical energy-storage systems

Graphene-Encapsulated Bifunctional Catalysts with High Activity and Durability for Zn-Air Battery

Carbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn-air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn-air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ?E value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm(-2) in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn-air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices

Rational Design of a High Performance and Robust Solar Evaporator via 3D-Printing Technology

Utilizing the broad-band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar-to-vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost-effective approaches: I) a rational design of a concave shaped supporter by 3D-printing that can promote the light harvesting capacity via multiple reflections on the surface; II) the use of a double layered photoabsorber composed of a hydrophilic bottom layer of a polydopamine (PDA) coated glass fiber (GF/C) and a hydrophobic upper layer of a carbonized poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogel on the supporter, which provides competitive benefit for preventing deposition of salt while quickly pumping the water. The 3D-printed solar evaporator can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m(-2) h(-1) and efficiency of 89% under 1 sun irradiation. The underlying reason for the high efficiency obtained is supported by the heat transfer mechanism. The 3D-printed solar evaporator could provide cheap drinking water in remote areas, while maintaining stable performance for a long term

Graphitization with Suppressed Carbon Loss for High-Quality Reduced Graphene Oxide

An efficient reduction method to obtain high-quality graphene sheets from mass-producible graphene oxide is highly desirable for practical applications. Here, we report an in situ deoxidation and graphitization mechanism for graphene oxide that allows for high-quality reduced graphene oxide sheets under the low temperature condition (&lt;300 degrees C) by utilizing a well-known Fischer-Tropsch reaction catalyst (CuFeO2). By applying modified FTR conditions, where graphene oxide was reduced on the catalyst surface under the hydrogen-poor condition, deoxidation with much suppressed carbon loss was possible, resulting in high-quality graphene sheets. Our experimental data and density functional theory calculations proved that reduction which occurred on the CuFeO2 surface preferentially removed adsorbed oxygen atoms in graphene oxide sheets, leaving dissociated carbon structures to be restored to a near-perfect few-layer graphene sheet. TGA-mass data revealed that GO with catalysts released 92.8% less carbon-containing gases than GO without catalysts during the reduction process, which suggests that this process suppressed carbon loss in graphene oxide sheets, leading to near-perfect graphene. The amount of oxygen related to the epoxide group in the basal plane of GO significantly decreased to near zero (from 43.84 to 0.48 at. %) in catalyst-assisted reduced graphene oxide (CA-rGO). The average domain size and the density of defects of CA-rGO were 4 times larger and 0.1 times lower than those for thermally reduced graphene oxide (TrGO), respectively. As a result, CA-rGO had a 246 and 8 times lower electrical resistance than TrGO and CVD-graphene. With these performances, CA-rGO coated paper connected to a coin-cell battery successfully lit an LED bulb, and CA-rGO itself acted as an efficient catalyst for both the hydrogen evolution reaction and the oxygen evolution reaction

Graphitization with Suppressed Carbon Loss for High-Quality Reduced Graphene Oxide (vol 15, pg 11655, 2021)

An efficient reduction method to obtain high-quality graphene sheets from mass-producible graphene oxide is highly desirable for practical applications. Here, we report an in situ deoxidation and graphitization mechanism for graphene oxide that allows for high-quality reduced graphene oxide sheets under the low temperature condition (<300 °C) by utilizing a well-known Fischer–Tropsch reaction catalyst (CuFeO2). By applying modified FTR conditions, where graphene oxide was reduced on the catalyst surface under the hydrogen-poor condition, deoxidation with much suppressed carbon loss was possible, resulting in high-quality graphene sheets. Our experimental data and density functional theory calculations proved that reduction which occurred on the CuFeO2 surface preferentially removed adsorbed oxygen atoms in graphene oxide sheets, leaving dissociated carbon structures to be restored to a near-perfect few-layer graphene sheet. TGA-mass data revealed that GO with catalysts released 92.8% less carbon-containing gases than GO without catalysts during the reduction process, which suggests that this process suppressed carbon loss in graphene oxide sheets, leading to near-perfect graphene. The amount of oxygen related to the epoxide group in the basal plane of GO significantly decreased to near zero (from 43.84 to 0.48 at. %) in catalyst-assisted reduced graphene oxide (CA-rGO). The average domain size and the density of defects of CA-rGO were 4 times larger and 0.1 times lower than those for thermally reduced graphene oxide (TrGO), respectively. As a result, CA-rGO had a 246 and 8 times lower electrical resistance than TrGO and CVD-graphene. With these performances, CA-rGO coated paper connected to a coin-cell battery successfully lit an LED bulb, and CA-rGO itself acted as an efficient catalyst for both the hydrogen evolution reaction and the oxygen evolution reaction.11Nsciescopu