Potassium-chemical synthesis of 3D graphene from CO2 and its excellent performance in HTM-free perovskite solar cells

The conversion of greenhouse gas CO2 into novel materials is the most promising approach to solve greenhouse gas issues. Herein, we report for the first time the reaction of potassium with CO2 to synthesize three-dimensional honeycomb-like structured graphene (3DHG). Furthermore, 3DHG exhibited excellent performance as a counter electrode for hole transport material (HTM)-free perovskite solar cells, leading to a power conversion efficiency of 10.06%. This work constitutes a new aspect of potassium chemistry for material synthesis from a greenhouse gas and the generation of electrical energy from sunlight.Fil: Wei, Wei. Michigan Technological University; Estados UnidosFil: Hu, Baoyun. Tongji University; ChinaFil: Jin, Fangming. Shanghai Jiao Tong University; ChinaFil: Jing, Zhenzi. Tongji University; ChinaFil: Li, Yuexiang. Nanchang University; ChinaFil: Garcia Blanco, Andres Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada ; ArgentinaFil: Stacchiola, Dario Jose. Brookhaven National Laboratory; Estados UnidosFil: Hu, Yun Hang. Michigan Technological University; Estados Unido

Monitoring of atopic dermatitis using leaky coaxial cable

In our daily life, inadvertent scratching may increase the severity of skin diseases (such as atopic dermatitis, etc.). However, people rarely pay attention to this matter, so the known measurement behavior of the movement is also very little. Nevertheless, the behavior and frequency of scratching represent the degree of itching, and the analysis of scratching frequency is helpful to the doctor's clinical dosage. In this paper, a novel system is proposed to monitor the scratching motion of a sleeping human body at night. The core device of the system are just a Leaky coaxial cable (LCX) and a router. Commonly, LCX is used in the blind field or semi blind field in wireless communication. The new idea is that the leaky cable is placed on the bed, then the state information of physical layer of wireless communication channels is acquired to identify the scratching motion and other small body movements in the human sleep process. The results show that it can be used to detect the movement and its duration. Channel state information (CSI) packet is collected by card installed in the computer based on the 802.11n protocol. The characterization of the scratch motion in the collected channel state information is unique, so it can be distinguished from the wireless channel amplitude variation trend

Biometric behavior authentication exploiting propagation characteristics of wireless channel

Massive expansion of wireless body area networks (WBANs) in the field of health monitoring applications has given rise to the generation of huge amount of biomedical data. Ensuring privacy and security of this very personal data serves as a major hurdle in the development of these systems. An effective and energy friendly authentication algorithm is, therefore, a necessary requirement for current WBANs. Conventional authentication algorithms are often implemented on higher levels of the Open System Interconnection model and require advanced software or major hardware upgradation. This paper investigates the implementation of a physical layer security algorithm as an alternative. The algorithm is based on the behavior fingerprint developed using the wireless channel characteristics. The usability of the algorithm is established through experimental results, which show that this authentication method is not only effective, but also very suitable for the energy-, resource-, and interface-limited WBAN medical applications

Carbohydrates generated via hot water as catalyst for CO2 reduction reaction

Combining terrestrial biomass with submarine-type hydrothermal environments for CO2 reduction is a possible approach for realizing new energies while achieving sustainable circulation of carbon. Herein, carbohydrateenabled CO2 reduction based on NaHCO3 conversion to formate revealed that hydrothermal environments facilitated direct hydrogen transfer from carbohydrates (glucose, cellulose) to CO2/NaHCO3 with hot water (250–300 °C, 5–20 MPa) acting as homogeneous catalyst in absence of any conventional catalysts giving CO2/ NaHCO3 reduction efficiencies as high as 76% for cellulose. Time-resolved operando hydrothermal DRIFTS spectra of glycolaldehyde in hot water (250 °C, autogenous pressure) verified that water catalyzed NaHCO3 reduction by converting the -CHO group in the carbohydrate to its hydrated state as -CH(OH)2, which enabled NaHCO3 reduction by direct hydrogen transfer and that the ratio of hydrogen transfer from water:- glycolaldehyde for NaHCO3 reduction was about 13:87 on an atom basis. For cellulose exploited as energy input, a greater than 3.4% solar-to-formate efficiency can be theoretically attained, which is unprecedented compared with present literature values. These findings provide basic data for future studies on biomass-enabled CO2 reduction and broaden the scope of hydrothermal chemistry for developing net-zero emission processes

Double threshold authentication using body area radio channel characteristics

The demand of portable and body-worn devices for remote health monitoring is ever increasing. One of the major challenges caused by this influx of wireless body area network (WBAN) devices is security of user's extremely vital and personal information. Conventional authentication techniques implemented at upper layers of the Open System Interconnection (OSI) model usually consumes huge amount of power. They also require significant changes at hardware and software levels. It makes them unsuitable for inherently low powered WBAN devices. This letter investigates the usability of a double threshold algorithm as a physical layer security measure in these scenarios. The algorithm is based on the user's behavioral fingerprint extracted from the radio channel characteristics. Effectiveness of this technique is established through experimental measurements considering a variety of common usage scenarios. The results show that this method provides high level of security against false authentication attacks and has great potential in WBANs

Antenna and Propagation Considerations for Amateur UAV Monitoring

The broad application spectrum of unmanned aerial vehicles is making them one of the most promising technologies of Internet of Things era. Proactive prevention for public safety threats is one of the key areas with vast potential of surveillance and monitoring drones. Antennas play a vital role in such applications to establish reliable communication in these scenarios. This paper considers line-of-sight and non-line-of-sight threat scenarios with the perspective of antennas and electromagnetic wave propagation

Sleep apnea syndrome sensing at C-Band

A non-intrusive sleep apnea detection system using a C-Band channel sensing technique is proposed to monitor sleep apnea syndrome in real time. The system utilizes perturbations of RF signals to differentiate between patient's breathing under normal and sleep apnea conditions. The peak distance calculation is used to obtain the respiratory rates. A comparison of the datasets generated by the proposed method and a wearable sensor is made using a concordance correlation coefficient to establish its accuracy. The results show that the proposed sensing technique exhibits high accuracy and robustness, with more than 80% concordance with the wearable breathing sensor. This method is, therefore, a good candidate for the real-time wireless detection of sleep apnea

Patterns-of-Life Aided Authentication

Wireless Body Area Network (WBAN) applications have grown immensely in the past few years. However, security and privacy of the user are two major obstacles in their development. The complex and very sensitive nature of the body-mounted sensors means the traditional network layer security arrangements are not sufficient to employ their full potential, and novel solutions are necessary. In contrast, security methods based on physical layers tend to be more suitable and have simple requirements. The problem of initial trust needs to be addressed as a prelude to the physical layer security key arrangement. This paper proposes a patterns-of-life aided authentication model to solve this issue. The model employs the wireless channel fingerprint created by the user’s behavior characterization. The performance of the proposed model is established through experimental measurements at 2.45 GHz. Experimental results show that high correlation values of 0.852 to 0.959 with the habitual action of the user in different scenarios can be used for auxiliary identity authentication, which is a scalable result for future studies

Breathing Rhythm Analysis in Body Centric Networks

Respiratory rhythm is the marker of respiratory diseases. A compromised respiratory system can be life threatening and potentially cause damage to other organs and tissues. However, most people do not realize the importance of respiratory rhythm detection because of expensive and limited medical conditions. In this paper, we present a noncontact and economically viable respiratory rhythm-detection system using S-band sensing technique. The system leverages microwave sensing platform to capture the minute variations caused by breathing. Subsequently, we implement data preprocessing and respiratory rate estimation for acquired wireless data to achieve respiratory rhythm detection. The experimental results not only validate the feasibility of respiratory rhythm detection using S-band sensing technique but also demonstrate that the S-Breath system provides a good performance