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By introducing a heteroatom into carbon material, an effective improvement in capacitance can be realized owing to surface oxidation and reduction reactions of pseudocapacitors. Herein, a simple one-pot carbonization activation method was proposed to convert potassium citrate into three-dimensional interconnected porous carbon (PC). Then, an effective double heteroatom doping method by thiourea was used to prepare nitrogen-sulfur-doped PC (N,S-PC). This porous structure facilitates the storage of a large number of ions and reduces their diffusion path. The synthesized N,S-PC nanomaterial has a capacitance of 674 F/g at 1 A/g in a 1 M H

Tetradymite-structured chalcogenides, such as Bi2Te3 and Sb2Te3, are quasi-two-dimensional (2D) layered compounds, which are significant thermoelectric materials applied near room temperature. The intercalation of guest species in van der Waals (vdW) gap implemented for tunning properties has attracted much attention in recent years. We attempt to insert Ga atoms in the vdW gap between the Te layers in p-type Bi0.3Sb1.7Te3 (BST) for further improving thermoelectrics. The vdW-related defects (including extrinsic interstitial and intrinsic defects) induced by Ga intercalation can not only modulate the carrier concentration but enhance the texture, thereby yielding excellent electrical properties, which is reflected in the power factor PF ~4.43 mW m-1 K-2. Furthermore, the intercalation of Ga produces multi-scale lattice imperfections such as point defects, Te precipitations, and nanopores, realizing the low lattice thermal conductivity in BST-Ga samples. Ultimately, a peak zT ~1.1 at 373 K is achieved in the BST-1%Ga sample and greatly improved by ~22% compared to the pristine BST. The weak bonding of vdW interlayer interaction can boost the synergistic effect for advancing BST-based or other layered thermoelectrics.

The grand challenge toward the miniaturization of untethered robots is the lack of a proper actuation system that can effectively transform the limited onboard energy into an untethered movement of the whole body. Here, in this article, we present an insect scale, 5-mm-long, and 9.4 mg in body mass untethered crawling robot powered by a 37 mg onboard ceramic capacitor. With high electromechanical efficiency by utilizing self-excited electrostatic vibration, the prototype device can be directly powered by an onboard capacitor without any boost or frequency conversion circuitry, and forward movements have been achieved at an average moving speed of 5.9 mm/s for 1.68 s. The maneuverability of locomotion from solid ground to water and different moving directional controls via the leg designs have been demonstrated for the advancements in the field of millimeter-scale robotics research.

Low temperature, microcube-shaped zinc stannate (ZnSnO3) nanostructures using a low-power microheater sensor platform to detect NO2 gas with high sensitivity and selectivity.

The lamellar structure of (Bi,Sb)2(Te,Se)3 alloys makes it difficult to achieve isotropic thermoelectric properties in the directions along and perpendicular to the c-axis, especially for n-type samples. In this work, by introducing Cu in polycrystalline n-type CuxBi2Te2.7Se0.3 and applying the traditional synthesis process of high-energy ball milling and hot pressing, substantial enhancement of the thermoelectric figure of merit zT is obtained in both in-plane and out-of-plane directions. The intercalated Cu not only provides electron transport media for mobility improvement but also reduces the lattice thermal conductivity owing to the strain fluctuation. Typically, the van der Waals gap in the out-of-plane direction leads to relatively slower mobility and lower lattice thermal conductivity. Taking into account the same average density-of-state effective mass (mavg* ∼ 1.5me) predicted based on a single parabolic model, the obtained quality factor β is comparable in both directions. As a result, a peak zT ∼ 1.05 at 420 K and the average zT approaching to 1.0 in the temperature range 300-500 K are obtained in both directions for the Cu0. 02Bi2Te2.7Se0.3 sample. The simple synthesis process and isotropic thermoelectric properties in this work make n-type Bi2Te3 more convenient for potential production and application.

Background: The Internet of things (IoT) connects all items to the Internet through information-sensing devices to exchange information for intelligent identification and management. Sybil attack is a famous and crippling attack in IoT. Most of the previous methods of detecting Sybil attacks in IoT mainly focus on static IoT while there are very rare methods applicable to mobile IoT. Results: In this paper, a novel, lightweight, and distributive detection scheme based on edge computing is proposed for detecting Sybil attacks in mobile IoT. In the proposed scheme, detection consists of two rounds. In each round, member nodes are required to send packets to edge nodes. Edge nodes calculate a possible interval of the received signal strength indication (RSSI) from the first round and check whether the RSSI from the second round is in the interval to detect Sybil attacks. Extensive experimental studies are included to show that the presented approach outperforms many existing approaches in terms of true detection and false detection rates.