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160 results on '"Wu, Dongmin"'

1. Multi-wavelength structured light based on metasurfaces for 3D imaging

Author

Lyu Baiying, Chen Chen, Wang Jian, Li Chang, Zhang Wei, Feng Yuxiang, Dong Fei, Zhang BaoShun, Zeng Zhongming, Wang Yiqun, and Wu Dongmin

Subjects
metasurface, structured light, multi-wavelength, three-dimensional imaging, resolution, Physics, QC1-999
Abstract

Structured light projection provides a promising approach to achieving fast and non-contact three-dimensional (3D) imaging. The resolution is a crucial index that represents security and accuracy in applications such as face recognition and robot vision. It depends on the density of dots in the projection. However, further improving the density of dots in the current system must be at the cost of speed or volume. Here, an all-dielectric ultra-thin metasurface is designed and fabricated to project a multi-wavelength dot array. The density of dots is improved because projected dots with different wavelengths fill the gaps with each other. The experimental results demonstrate that the multi-wavelength projection improves the resolution of 3D imaging. Furthermore, the multi-wavelength system is beneficial to measuring a surface with varying colors. The approach has the potential to achieve a new generation of high-resolution systems for tiny fluctuations and colorful 3D imaging in dark environments.

Published
2024
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4. High-efficiency spontaneous terahertz emission from electrically-excited plasmons in AlGaN/GaN two-dimensional electron gas

Author

Qin, Hua, Yu, Yao, Sun, Jiandong, Zheng, Zhongxin, Huang, Yongdan, Li, Xingxin, Zhou, Yu, Wu, Dongmin, Zhang, Zhipeng, Zeng, Cunhong, Cai, Yong, Zhang, Xiaoyu, Zhang, Baoshun, Tu, Xuecou, Zhou, Gaochao, Jin, Biaobing, Kang, Lin, Chen, Jian, and Wu, Peiheng

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The advance of terahertz science and technology yet lays wait for the breakthrough in high-efficiency and high-power solid-state terahertz sources applicable at room temperature. Plasmon in two-dimensional electron gas (2DEG) has long been pursued as a type of promising active medium for terahertz emitters. However, a high wall-plug efficiency sufficient for high-power operation has not been achieved. Here we report spontaneous terahertz emission tunable in a frequency range from 0.3 to 2.5 THz through electrical excitation of plasmon or plasmon-polariton modes in a grating-gate coupled AlGaN/GaN 2DEG at 7 K. A wall-plug efficiency ranging from $10^{-6}$ to $10^{-1}$ is found by tuning the energy (4.5 eV to 0.5 eV) of tunneling electrons between the grating gates and the 2DEG. The total emission power, albeit below 15 nW, is already detectable by using a direct terahertz field-effect transistor detector based on the same type of 2DEG. The findings indicate that both high-efficiency and high-power terahertz plasmon-polariton emission could be obtained by a proper injection of tunneling electrons with low energy and high current density., Comment: 4.5 pages, 4 figures

Published
2017

5. Pancharatnam-Berry phase induced spin-selective transmission in herringbone dielectric metamaterials

Author

Kenney, Mitchell, Li, Shaoxian, Zhang, Xueqian, Su, Xiaoqiang, Kim, Teun-Teun, Wang, Dongyang, Wu, Dongmin, Ouyang, Chunmei, Han, Jiaguang, Zhang, Weili, Sun, Hongbo, and Zhang, Shuang

Subjects
Physics - Optics
Abstract

Manipulating the polarisation of light is crucial for sensing and imaging applications. One such aspect in particular is selective transmission of one circular polarisation (spin) when light is transmitted through a medium or a device. However, most present methods of achieving this have relatively low efficiency and selectivity, whilst high selectivity examples rely on lossy and complex three-dimensional helical or multilayer structures. Here, we propose a dielectric metamaterial approach for achieving spin-selective transmission of electromagnetic waves, utilizing spin-controlled constructive or destructive interference between two Pancharatnam-Berry (PB) phases in conjunction with propagative dynamic phase. The dielectric metamaterial, consisting of monolithic silicon herringbone structures, exhibits a broadband operation in the terahertz regime whilst obtaining a spin-selective efficiency upwards of 60%. Such a device is robust and is not easily degraded by errors in fabrication., Comment: 15 pages, 4 figures, Advanced Materials, first published: 14 September 2016

Published
2016
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11. Lock-In Amplifier With Enhanced Filter Structure for NMR Gyroscope

Author

Wang, Zhengguang, Liu, Nan, Ding, Peng, Ji, Yafei, Ru, Zhanqiang, Yin, Zhizhen, Wu, Dongmin, and Song, Helun

Abstract

To maintain the functionality of the nuclear magnetic resonance (NMR) gyroscope, extracting the precession phase and compensating for the transverse driving field is essential. The digital lock-in amplifier (DLIA) effectively captures amplitude and phase information from weak signals. The performance of the low-pass filter (LPF) within the DLIA is significant. To achieve high precision, the finite impulse response (FIR) filter requires an extremely low cut-off frequency, which results in higher order, complex operations, and significant resource consumption. The moving average filter (MAF) has high attenuation at specific frequencies and low attenuation at others. Meanwhile, lengthy windows result in increased resource consumption, higher latency, and the inability to capture rapidly changing signals. To address these challenges, a cascade filter structure is proposed, where a low-order FIR filter is cascaded with a small window MAF. This structure utilizes the FIR filter for high stopband attenuation, while the MAF further attenuates at specified frequencies and narrows the transition band. Consequently, this improvement effectively reduces the FIR filter order and MAF window length, preventing the attenuation of swiftly changing signals caused by extended window lengths. To minimize resource consumption, a dual FIR filters resource optimization method is introduced based on time-division multiplexing (TDM) and parallel distributed algorithms (PDAs), allowing two FIR filters to share one coefficient table. Subsequently, the performance of the proposed DLIA is evaluated under various conditions and implemented in a field-programmable gate array (FPGA). The results indicate that the proposed DLIA exhibits superior performance, low computational complexity, and low resource utilization.

Published
2024
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14. Application of Particle Swarm Optimization and Ant Colony Optimization integration in the Aerator Reducer Optimization Design

Author

Wu Dongmin, Rui Yannian, and Shen Ming

Subjects
Planetary gear reducer, PSO, ACO, PAAA, Optimization design, Mechanical engineering and machinery, TJ1-1570
Abstract

The Ant colony algorithm has the defects of premature convergence as its parameter selection greatly dependent on the personal experience.In order to solve the problem,a PAAA algorithm to optimization design the planetary gear reducer of the aerator is presented.To meet the constraints condition of structure and strength,taking the minimum volume and the highest efficiency of the planetary gear train as objective functions,its optimization mathematics model is established.The Matlab program is wrote to solve the mathematical model by using PAAA algorithm.The research results show that planetary gear train has smaller volume and higher efficiency under assuring the design requirements.The results also verified the PAAA optimization has the advantage of effective,accurate and reliable.

Published
2015
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18. Characterization of 87Rb MEMS vapor cells for miniature atomic magnetometers.

Author

Jiang, Minwei, Zhai, Hao, Jiang, Chunyu, Wang, Jian, Chen, Chen, Zhang, Qi, Wu, Dongmin, Zhang, Baoshun, Zeng, Zhongming, Lin, Jie, Wang, Yiqun, and Jin, Peng

Subjects
MAGNETOMETERS, VAPORS, MICROELECTROMECHANICAL systems, ANTIREFLECTIVE coatings, MAGNETIC fields, BIOMAGNETISM
Abstract

Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the 87Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the 87Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the 87Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments. [ABSTRACT FROM AUTHOR]

Published
2023
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21. Flexible Self‐Powered Photoelectrochemical Photodetector with Ultrahigh Detectivity, Ultraviolet/Visible Reject Ratio, Stability, and a Quasi‐Invisible Functionality Based on Lift‐Off Vertical (Al,Ga)N Nanowires (Adv. Mater. Interfaces 16/2022)

Author

Jiang, Min, primary, Zhang, Jianya, additional, Yang, Wenxian, additional, Wu, Dongmin, additional, Zhao, Yukun, additional, Wu, Yuanyuan, additional, Zhou, Min, additional, and Lu, Shulong, additional

Published
2022
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23. Flexural Vibration Magnetoelectric Antenna for Medium Frequency and High Frequency.

Author

Liu, Yizhang, Zeng, Zhongming, Lin, Wenkui, Yun, Xiaofan, Wu, Dongmin, Zha, Qiang, and Zhang, Baoshun

Subjects
HIGH frequency antennas, ANTENNAS (Electronics), ULTRASONIC transducers, ACOUSTIC radiation, ARTIFICIAL implants, WIRELESS communications, PIEZOELECTRIC transducers
Abstract

High-frequency (HF) and medium frequency (MF) antennas are an important part of modern wireless communication systems. However, the extremely large size of small electric antennas in these bands limits the range of applications of wireless communication systems, especially in implantable devices and the Internet of Things (IoT). In this article, a Microscale Flexible Vibration-Magnetoelectric (FV-ME) antenna with resonant frequencies at MF or HF is proposed. At MF or HF, the size of FV-ME is smaller than that of Magnetoelectric (ME) antennas based on other driving modes. The coupling mechanism of the FV-ME antenna is analyzed using an equivalent circuit. The equivalent circuit is formed by adding a force-magnetic coupling coefficient to the equivalent circuit of a piezoelectric micromechanical ultrasonic transducer, which is derived by the energy method. The effects of material coverage, thickness ratio, modulus ratio and acoustic radiation on the ME coefficient of the FV-ME were evaluated. These results show that ME antennas based on bending vibration modes can operate at intermediate or high frequencies. Furthermore, the FV-ME antenna having a diameter of hundreds of microns is significantly smaller than other MF or HF antennas. [ABSTRACT FROM AUTHOR]

Published
2023
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32. Anisotropic artificial synapse based on 2D ReS2 field-effect transistor.

Author

Wang, Qilitai, Lv, Wenxing, Cai, Jialin, Lv, Weiming, Lei, Ting, Cui, Boyao, Luo, Jun, Bian, Lifeng, Sun, Xuemei, Wu, Dongmin, Zhang, Baoshun, and Zeng, Zhongming

Subjects
FIELD-effect transistors, PROBLEM solving, CRYSTAL symmetry, OPTICAL modulation, SYMMETRY breaking, SYNAPSES
Abstract

Taking inspiration from the brain, neuromorphic systems are thought to be a potential computational platform to solve the problems of the "von-Neumann bottleneck." Artificial synaptic devices hold the potential to emulate the multi-synapse system to perform complex functions by applying anisotropic materials. Here, we demonstrate a synaptic device based on a two-dimensional ReS2 material, exhibiting synaptic functions such as short-term plasticity, long-term plasticity, paired-pulse facilitation, and spike-rate dependent plasticity. More importantly, benefiting from the broken symmetry of the ReS2 crystal, the devices showed obvious anisotropy of response behavior to the same input signal. In addition, the synaptic performance can also be modulated by laser irradiation. Our results provide possibilities for two-dimensional materials to mimic the biological axon-multisynapse systems with additional optical modulation. [ABSTRACT FROM AUTHOR]

Published
2021
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33. High-Efficiency Asymmetric Transmission of Circularly Polarized THz waves using a Dielectric Herringbone Metasurface

Author

Kenney, Mitchell Guy, Li, Shaoxian, Zhang, Xueqian, Kim, Teun-teun, Wang, Dongyang, Wu, Dongmin, Ouyang, Chunmei, Han, Jiaguang, Zhang, Weili, Sun, Hong-bo, and Zhang, Shuang

Subjects
TK, QC
Abstract

An interesting topic is that of metamaterials imparting chiral responses which invoke a disparity between opposite handednesses of circularly polarised (CP) light. Most chiral metamaterials are either 3D-helical structures [1] or stacked metallic structures with twisted orientations [2]. These structures allow selective transmission of one CP whilst prohibiting or reflecting the other, termed Circular Dichroism. However, for 2D chiral metamaterials, this is not so. Instead, the cross-polarisation conversion of one CP to another is different. The original work in [3] used an anisotropic lossy planar-chiral “fish-scale” structure to exhibit this effect, termed Asymmetric Transmission (AT). However, these responses are small with efficiencies less than 25%. Works to improve efficiency used 3D arrangements. Work in [4] achieved much higher efficiency than for the 2D planar-chiral structures, but due to the metallic construction absorption losses were unavoidable; such losses were given as 37%.\ud \ud Here, we propose a means of achieving AT using a loss-free mechanism at 1THz frequency by constructing Monolithic Herringbone metamaterials from a dielectric medium [5]. This device works by a spin-selective interference of CP light, due to Pancharatnam-Berry (PB) phases, in conjunction with a propagative dynamic phase (Fig. 2) causing constructive interference for TRL and destructive for TLR Jones matrix components. An analytical derivation (Fig. 1a) was found to agree well with numerical simulations (Fig. 1b) for the design. These results indicate a conversion efficiency of LCP to RCP (TRL) exceeding 80%. Fabrication of Intrinsic Silicon was used for the devices (Fig. 2) and THz Time Domain Spectroscopy (THz-TDS) was used to characterise the samples, showing a 60% spin-conversion efficiency (Fig. 3). Such a device is robust and is not easily degraded by errors in fabrication.

Published
2017

39. Unsupervised Learning for Lighting Control System

Author

Sepponen, Laura, Jung, Alexander, Perustieteiden korkeakoulu, Hirvisalo, Vesa, Wu, Dongmin, Sepponen, Laura, Jung, Alexander, Perustieteiden korkeakoulu, Hirvisalo, Vesa, and Wu, Dongmin

Abstract

Finding a balance point between the energy consumption and user experience is one of the most important tasks in current lighting control systems. For achieving that goal, finding resonalble group configuration of sensors/luminaires is necessary. However, most of the current lighting control systems use fixed group configuration based on empirical knowledge from human experts. This thesis uses time-series clustering, a specific method in the unsupervised learning, for exploring possible solutions of building a model that can find that balance point automatically and dynamically. For evaluating the clutering result of our model, this thesis proposes three evaluation methods specifically designed for the lighting control system, since this topic is relatively new in this industry. After testing with difierent combinations of tools, this thesis builds a model that proved to be useful for solving the problem of finding proper group configurations for lighting control system.

Published
2018

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