Ultralow detection limit of giant magnetoresistance biosensor using Fe_3O_4–graphene composite nanoparticle label

A special Fe_3O_4nanoparticles–graphene(Fe_3O_4–GN) composite as a magnetic label was employed for biodetection using giant magnetoresistance(GMR) sensors with a Wheatstone bridge. The Fe_3O_4–GN composite exhibits a strong ferromagnetic behavior with the saturation magnetization M_S of approximately 48 emu/g, coercivity H_C of 200 Oe, and remanence M_r of 8.3 emu/g, leading to a large magnetic fringing field. However, the Fe_3O_4 nanoparticles do not aggregate together, which can be attributed to the pinning and separating effects of graphene sheet to the magnetic particles. The Fe_3O_4–GN composite is especially suitable for biodetection as a promising magnetic label since it combines two advantages of large fringing field and no aggregation. As a result, the concentration x dependence of voltage difference |?V| between detecting and reference sensors undergoes the relationship of |?V| = 240.5 lgx + 515.2 with an ultralow detection limit of 10 ng/mL(very close to the calculated limit of 7 ng/mL) and a wide detection range of 4 orders.     

氮化镓基感光栅极高电子迁移率晶体管器件设计与制备

GaN基高电子迁移率晶体管(HEMT)作为栅控器件,具有AlGaN/GaN异质结处高浓度的二维电子气(2DEG)及对表面态敏感等特性,在栅位置处与感光功能薄膜的结合是光探测器领域重要的研究方向之一.本文首先提出在GaN基HEMT栅电极上引入光敏材料锆钛酸铅(PZT),将具有光伏效应的铁电薄膜PZT与HEMT栅极结合,提出一种新的"金属/铁电薄膜/金属/半导体(M/F/M/S)"结构;然后在以蓝宝石为衬底的AlGaN/GaN外延片上制备感光栅极HEMT器件.最后,通过PZT的光伏效应来调控沟道中的载流子浓度和通过源漏电流的变化来实现对可见光和紫外光的探测.在365 nm紫外光和普通可见光条件下,对比测试有/无感光栅极的HEMT器件,在较小V_(gs)电压时,可见光下测得前者较后者的饱和漏源电流I_(ds)的增幅不下降,紫外光下前者较后者的I_(ds)增幅大5.2 mA,由此可知,感光栅PZT在可见光及紫外光下可作用于栅极GaN基HEMT器件并可调控沟道电流.     

石英增强光声光谱技术研究进展

石英增强光声光谱（QEPAS）技术是一种新颖的气体探测技术,具有体积小、灵敏度高等优点,是痕量气体检测技术的研究热点。本文对QEPAS技术的基本原理、发展历史及发展现状进行了综述,并对多种不同结构的QEPAS系统发展情况进行了介绍,最后对该技术的发展前景进行了展望。     

Community detection in signed networks based on discrete-time model

Community detection in signed networks has been studied widely in recent years. In this paper, a discrete difference equation is proposed to imitate the consistently changing phases of the nodes. During the interaction, each node will update its phase based on the difference equation. Each node has many different nodes connected with it, and these neighbors have different influences on it. The similarity between two nodes is applied to describe the influences between them. Nodes with high positive similarities will get together and nodes with negative similarities will be far away from each other.Communities are detected ultimately when the phases of the nodes are stable. Experiments on real world and synthetic signed networks show the efficiency of detection performance. Moreover, the presented method gains better detection performance than two existing good algorithms.     

Quantum interference between heralded single photon state and coherent state

Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.     

A generalized model of TiO_x-based memristive devices and its application for image processing

Memristive technology has been widely explored, due to its distinctive properties, such as nonvolatility, high density,versatility, and CMOS compatibility. For memristive devices, a general compact model is highly favorable for the realization of its circuits and applications. In this paper, we propose a novel memristive model of TiO_x-based devices, which considers the negative differential resistance(NDR) behavior. This model is physics-oriented and passes Linn's criteria. It not only exhibits sufficient accuracy(IV characteristics within 1.5% RMS), lower latency(below half the VTEAM model),and preferable generality compared to previous models, but also yields more precise predictions of long-term potentiation/depression(LTP/LTD). Finally, novel methods based on memristive models are proposed for gray sketching and edge detection applications. These methods avoid complex nonlinear functions required by their original counterparts. When the proposed model is utilized in these methods, they achieve increased contrast ratio and accuracy(for gray sketching and edge detection, respectively) compared to the Simmons model. Our results suggest a memristor-based network is a promising candidate to tackle the existing inefficiencies in traditional image processing methods.     

基于外差法的光纤激光器相干合成

采用波长1064 nm,功率为1 W的种子激光实现了两路光纤激光的相干合成,采用了两只保偏光纤准直器接收两路光干涉信号,与利用透镜直接把干涉信号会聚在探测器上相比,这种耦合方式得到的光干涉信号的条纹对比度更高。对相位噪声以及相位噪声的带宽进行了研究,结果表明,相位噪声由电信号串扰以及环境扰动产生。通过人为拨动光纤来增加相位噪声带宽,当相位噪声带宽增加时,相位控制精度下降。提出了提高相位控制精度的方法,实验获得了桶中功率为21.3%、斯特列尔比为79%、相位控制精度为0.008的相干合成效果。     

一种基于奇异谱的语音激活检测方法

为了提高语音激活检测在低信噪比环境中的检测性能,提出了一种基于奇异谱的语音激活检测方法。首先用多窗口方法计算每一帧语音信号的相关矩阵;然后对相关矩阵进行奇异值分解;利用奇异值可以反映有用信号和噪声分布情况的特性,将每一帧语音信号经过加权处理后的最大奇异值与自适应阈值进行比较进行语音激活检测。该方法原理简单,易于硬件实现,通过实验仿真表明,在低信噪比环境下,和基于对数能量方法相比,本文方法也能够很好的区分语音段和非语音段,有良好的检测性能。     

Analysis of atom detection via the magnetic optical effect

We demonstrated a new method of atom detection by means of the magnetic optical effect. The number density of the atom cloud was measured by detecting the rotation angle of the polarization plane of linearly polarized probe light when propagating inside the atomic cloud. Detuning, the magnetic field and light intensity dependencies of the rotation angle were studied theoretically and experimentally to find the best parameter for atom detection. In this way, we managed to achieve a rotation angle of 0.22 rad with a signal to noise ratio (SNR) of 75 and a contrast of 87.5%.     

基于耦合Duffing振子的局部放电信号检测方法研究

以双向环形耦合Duffing振子系统为对象, 研究脉冲信号激励下耦合振子间动力学行为变化特征时, 发现其与单向环形耦合Duffing振子系统类似, 在一定的参数条件下, 脉冲信号能引起其中一个振子与其他振子运动轨迹间出现短暂失同步的现象即瞬态同步突变现象. 基于这种现象, 提出了一种微弱脉冲信号检测的新方法, 用于检测强噪声背景中的局部放电脉冲信号. 实验测试表明, 利用本文方法对不同放电电极的局部放电脉冲信号进行检测时, 在低信噪比条件下可取得良好的检测效果, 进而扩展了现有的Duffing振子对非周期信号的检测范围及应用领域. 关键词： 耦合Duffing 振子 微弱信号检测 瞬态同步突变 局部放电脉冲信号