Publications

A Battery‐Like Self‐Charge Universal Module for Motional Energy Harvest

Abstract Wearable and portable electronics have brought great convenience. These battery‐powered commercial devices have a limited lifetime and require recharging, which makes more extensive applications challenging. Here, a battery‐like self‐charge universal module (SUM) is developed, which is able to efficiently convert mechanical energy into electrical energy and store it in one device. An integrated SUM consists of a power management unit and an energy harvesting unit. Compared to other mechanical energy harvesting devices, SUM is more ingenious, efficient and can be universally used as a battery. Under low frequency (5 Hz), a SUM can deliver an excellent normalized output power of 2 mW g −1 . After carrying several SUMs and jogging for 10 min, a commercial global positioning system module is powered and works continuously for 0.5 h. SUMs can be easily assembled into different packages for powering various commercial electronics, demonstrating the great application prospects of SUM as a sustainable battery‐like device for wearable and portable electronics.

Nacelle Aerodynamic Optimization and Inlet Compatibility

The design of air induction system is targeting to balance the internal and external flow characteristics as well as the structure and aerodynamic integrity. An optimized air intake design that providing velocity and pressure distributions with least drag and maximum pressure recovery could end up at the expense of higher inlet flow distortion and lower stability margin. Indeed, design requirements and considerations at different operating conditions, such as takeoff, and high AOA maneuvers, could be significantly different from that of cruise and level flight. One of the most challenged operating conditions to be certified for FAR33 & FAR25 requirements is ground crosswind condition, when “Engine” is operating statically on the ground with high crosswind presented. It could accommodate inlet separation or distortion resulted from crosswind, and triggers fan or core stall, as well as induces high fan and/or engine vibrations. Studies of engine inlet compatibility become one of the major tasks required during the engine developing phase. This research is a parametric study of using CFD to evaluate operational characteristics of the air induction system. Comparisons of various inlet designs are made and characterized into four categories, i.e., i) Inlet pressure loss, ii) Nacelle drag, iii) Inlet flow distortion, and iv) Inlet Mach distribution. The objective is to assess the impact of air induction design of turbofan upon inlet compatibility. The research introduces the Kriging model and weighting coefficients to optimize internal total pressure loss and external drag using the isolated nacelle model. Bezier equation was used to fit the optimized curves obtained by changing several control points of the baseline configuration of nacelle. To study the impact of asymmetric lip on flow separation in ground crosswind condition, the paper built crosswind model which introduce a inlet boundary as fan face. Comparisons are then made between the original and optimal nacelle, to show correlation between inlet compatibility and air intake profile.

Stacking Faults in Formation of Silver Nanodisks

Structural investigations by using high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of silver nanodisks with different sizes are presented. The disks have a face centered cubic (fcc) crystal structure and their flat surfaces are (111). Stacking faults parallel to the (111) planes are frequently observed for the nanodisks. A unique (111) stacking fault model which is parallel to the flat (111) disk surface has been proposed to explain the observed 1/3{422} forbidden reflections in [111] SAED pattern and the corresponding 3×{422} supperlattice fringes in the [111] HRTEM image. It is suggested that the presence of the stacking faults may be the key in the formation and growth of the disk morphology. This study may provide an insight to synthetically controlling particle shape and size through defect engineering.

Design and analysis of photonic crystal spectral diversity filters for biosensing

We present a systematic method for designing spectral diversity filters using 2D and 3D photonic crystals. These filters convert an incoherent input beam with uniform spectral content over the input dimension into a desired nonuniform spatial-spectral pattern. Such spectral diversity filters can be used for designing compact spectrometers that can be used for the detection of Raman signatures in biosensors.

Largely Improved Near-Infrared Silicon-Photosensing by the Piezo-Phototronic Effect

Although silicon (Si) devices are the backbone of modern (opto-)electronics, infrared Si-photosensing suffers from low-efficiency due to its limitation in light-absorption. Here, we demonstrate a large improvement in the performance, equivalent to a 366-fold enhancement in photoresponsivity, of a Si-based near-infrared (NIR) photodetector (PD) by introducing the piezo-phototronic effect via a deposited CdS layer. By externally applying a −0.15‰ compressive strain to the heterojunction, carrier-dynamics modulation at the local junction can be induced by the piezoelectric polarization, and the photoresponsivity and detectivity of the PD exhibit an enhancement of two orders of magnitude, with the peak values up to 19.4 A/W and 1.8 × 1012 cm Hz1/2/W, respectively. The obtained maximum responsivity is considerably larger than those of commercial Si and InGaAs PDs in the NIR waveband. Meanwhile, the rise time and fall time are reduced by 84.6% and 76.1% under the external compressive strain. This work provides a cost-effective approach to achieve high-performance NIR photosensing by the piezo-phototronic effect for high-integration Si-based optoelectronic systems.

Recent progress on Maxwell's equations for a mechano-driven medium system for multi-moving-objects/media

Maxwell's equations for a mechano-driven media system (MEs-f-MDMS) have been developed for describing the electromagnetism of multi-slow-moving-media that may move with acceleration following complex trajectories.The approach starts from the integral forms of the four physics laws,and is different from the classical approach of using Lorentz transformation for correlating the electromagnetic phenomena observed in two inertia reference frames that have a relative motion. The governing equations inside the moving object/medium are the MEs-f-MDMS,and those in vacuum are the classical Maxwell's equations;the full solutions of both meet at the medium surface/interface and satisfy the boundary conditions. This paper reviews the background, physical principle,and mathematical derivations for formulating the MEs-f-MDMS. Strategies are also presented for mathematically solving the MEs-f-MDMS. The unique advances made by the MEs-f-MDMS have been systematically summarized and their potential applications in engineering are elaborated. We found that the Lorentz transformation is perfect for treating the electromagnetic phenomena of moving point charges in vacuum;but for moving objects,the covariance of the Maxwell's equations may not hold,and one may have to use MEs-f-MDMS if the moving velocity is low. Finally,recent advances for treating the boundary conditions at nano-scale without assuming an abrupt boundary are also reviewed.

Toward Robust Nanogenerators Using Aluminum Substrate

Nanogenerators (NG) have been developed to harvest mechanical energy from environmental sources such as vibration, human motion, or movement of automobiles. We demonstrate a robust and large-area NG based on a cost-effective Al substrate with the capability to be easily integrated in series and parallel for high-output performance. The output voltage and current density of the three-dimensionally integrated NG device reaches up to 3 V and 195 nA under human walking conditions.

Neurological Aspects of Cretinism in Qinghai Province

Multiwall Carbon Nanotubes Made of Monochirality Graphite Shells

A multiwall carbon nanotube (MWCNT) consists of several or many concentric carbon shells, each of which could be metallic or semiconducting. Both theoretical predictions and experimental results suggest that MWCNTs have exotic electronic structures and intriguing transport properties, which are highly dependent on chirality of each shell. However, the structural defects and the random distribution of chirality of each concentric graphitic shell make the MWCNTs difficult for basic research and technological applications. Thus far, it is still a challenge to get the high crystalline MWCNTs with limited atomic conformation. Here, we report the synthesis of high crystalline MWCNTs made of monochirality graphite shells by a low-temperature chemical vapor deposition (CVD) process in plasma environment. Structural analysis, carried out by transmission electron microscopy (TEM) image and electron diffraction methods, reveal that the MWCNTs are well-crystallized and that most of them have nearly identical chiralities.

Triboelectric Nanogenerator as a Probe for Studying Liquid Charge Transfer

Continuum Model for Coupled Acousto-Optical Phonons in Piezoelectric Materials

Achieving High Power Density and Durability of Multilayered Swing‐Structured Triboelectric Nanogenerator toward Marine Environmental Protection

Abstract Protecting marine environment is an important and urgent task to maintain marine ecological balance. As a promising blue energy harvesting technology, triboelectric nanogenerator (TENG) can provide electrical energy for marine environmental protection. Previous reported swing‐structured TENGs have advantages of low driving force in low‐frequency water waves and strong durability, but the space utilization and volume power density are relatively low. Here, a multilayered swing‐structured TENG (MS‐TENG) with low wear is designed to increase the space utilization rate, and thereby enhance the output performance. The MS‐TENG generates the highest peak power density of 15.18 W m −3 Hz −1 and average power density of 3.56 W m −3 Hz −1 under water wave triggering at 0.8 Hz. By coupling the charge pumping and non‐contact mode of main TENGs, the MS‐TENG achieves strong performance stability, exhibiting little attenuation of electric output after 240 000 cycles. Furthermore, the MS‐TENG has successfully powered a water quality detector for self‐powered ballast water quality monitoring, and an application is presented about electrical dehydration of water‐in‐oil emulsions driven by the MS‐TENG with a dehydration rate of 99.6%. This work promotes the development of high power density MS‐TENG and demonstrates its application potential for self‐powered marine environmental protection.

Piezo-Phototronic Effect on Photodetector

LD-Parser

Dependency parsing is one of the basic research of natural language processing. In recent years, transition-based and graph-based methods have been used widely, but there are still some problems such as feature limitation and high time complexity. In this paper, we proposed a new method named Leaf Detection based Dependency Parsing (LD-Parser), which is a bottom-up framework to detect leaf nodes of the dependency parsing tree. We use LSTM to construct a classifier to generate labels for each word and then remove the leaf nodes that are adjacent to their corresponding parents. Besides, an attention mechanism is introduced to sum the children of nodes as an extra feature according to the attention weight. We make experiments on Universal Dependencies in several languages. Experiments show that the LD-Parser with Attention performs better than transition-based and graph-based methods in dependency parsing tasks for short sentences.

Optimization of novel di-substituted cyclohexylbenzamide derivatives as potent 11β-HSD1 inhibitors

Perovskite Wide‐Angle Field‐Of‐View Camera

Researchers have attempted to create wide-angle field-of-view (FOV) cameras inspired by the structure of the eyes of animals, including fisheye and compound eye cameras. However, realizing wide-angle FOV cameras simultaneously exhibiting low distortion and high spatial resolution remains a significant challenge. In this study, a novel wide-angle FOV camera is developed by combining a single large-area flexible perovskite photodetector (FP-PD) using computational technology. With this camera, the proposed single-photodetector imaging technique can obtain high-spatial-resolution images using only a single detector, and the large-area FP-PD can be bent further to collect light from a wide-angle FOV. The proposed camera demonstrates remarkable features of an extraordinarily tunable wide FOV (greater than 150°), high spatial resolution of 256 × 256 pixels, and low distortion. It is believed that the proposed compatible and extensible camera prototype will promote the development of high-performance versatile FOV cameras.

Decoding ripple formation in single-layer transition metal chalcogenide lateral heterojunctions towards novel optoelectronic properties

Paper‐Based Supercapacitors for Self‐Powered Nanosystems

Energy storage on paper: Paper-based, all-solid-state, and flexible supercapacitors were fabricated, which can be charged by a piezoelectric generator or solar cells and then discharged to power a strain sensor or a blue-light-emitting diode, demonstrating its efficient energy management in self-powered nanosystems (see picture). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.