Lévy Flights, 1/<i>f </i>Noise and Self Organized Criticality

A new analysis of a previously studied traveling agent model, showed that there is a relation between the degree of homogeneity of the medium where the agents move, agent motion patterns, and the noise generated from their displacements. We proved that for a particular value of homogeneity, the system self organizes in a state where the agents carry out Lévy walks and the displacement signal corresponds to 1/f noise. Using probabilistic arguments, we conjectured that 1/f noise is a fingerprint of a statistical phase transition, from randomness (disorder) to predictability (order), and that it emerges from the contextuality nature of the system which generates it.

Random noise attenuation by f–x spatial projection-based complex empirical mode decomposition predictive filtering

The frequency–space（f–x） empirical mode decomposition（EMD） denoising method has two limitations when applied to nonstationary seismic data. First, subtracting the first intrinsic mode function（IMF） results in signal damage and limited denoising. Second, decomposing the real and imaginary parts of complex data may lead to inconsistent decomposition numbers. Thus, we propose a new method named f–x spatial projection-based complex empirical mode decomposition（CEMD） prediction filtering. The proposed approach directly decomposes complex seismic data into a series of complex IMFs（CIMFs） using the spatial projection-based CEMD algorithm and then applies f–x predictive filtering to the stationary CIMFs to improve the signal-to-noise ratio. Synthetic and real data examples were used to demonstrate the performance of the new method in random noise attenuation and seismic signal preservation.

1/f~γ Noise Characteristics of an n-MOSFET Under DC Hot Carrier Stress

The 1/fγ noise characteristic parameter Sfγ model in an n-MOSFET under DC hot carrier stress is studied. A method characterizing the MOSFET abilities of an anti-hot carrier with noise parameter Sfγ is presented. The hot carrier degradation effect of n-MOSFET in high-,mid-,and low gate stresses and its 1/fγ noise feature are studied. Experimental results agree well with the developed model.

Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 700 Gy（Si）. The low dose rate was 0.001 Gy（Si）/s and the high dose rate was 0.1 Gy（Si）/s. The model accords well with the experimental results.

一种基于改进f-k滤波的编码雷达信号去噪方法

超宽带编码雷达探测地下介质时,回波信号不可避免地受到噪声影响,这会对数据解释带来一定困难.频率-波数(f-k)滤波方法可以有效滤除部分噪声,但其对高频段的滤波效果欠佳.针对此问题,本文提出一种改进的f-k滤波方法,即根据频率和波数的分布情况,设置不同的视速度阈值进行分段处理,提高高频段的视速度阈值,有效滤除了高频段的噪声.实验结果表明,经本文方法处理后的图像熵较传统方法处理后的图像熵减小了6%,具有良好的噪声抑制效果.

三峡船闸北1#竖井f16断层综合处理技术

三峡永久船闸基础虽为前震旦纪侵入形成的闪云斜长花岗岩体 ,但经后期多次复合构造运动的影响 ,岩脉的侵入 ,裂隙、断层的切割 ,使基岩的完整性大大降低 ,地质构造复杂。通过对北 1# 竖井南侧井壁f16断层处理方案的合理的选择 ,在开挖支护的基础上 ,大胆对其上部结构改型 ,岩体与结构采用预应力高强锚杆连接 ,达到了预期的目的 ,为类似地质缺陷的处理提供了思路。

1/f噪声及其在二维材料石墨烯中的研究进展

1/f噪声具有丰富的物理内涵,既是科学研究的量化工具,也是电子器件重要性能指标.本文从通用数学形式和物理背景两个方面归纳总结1/f噪声模型.首先介绍了基于马尔可夫过程和基于扩散过程的1/f噪声通用数学模型.在此基础上,溯源1/f噪声物理模型的发展历程,总结五类典型物理模型,包括Mc Whorter模型、Hooge模型、Voss-Clarker模型、Dutta-Horn模型、干涉模型以及Hung统一模型.二维材料石墨烯让1/f噪声研究重归学术热点,本文梳理了当前石墨烯1/f噪声研究中形成的共识性研究成果,提出石墨烯低频噪声研究的三层次分类分析模型,分析了不同层面噪声机理研究代表性成果,归纳总结了各层面可能的主导机制.通过比较不同团队报道的石墨烯1/f噪声栅极调控特征谱型及测试条件,分析了复杂多变栅控谱型形成原因.基于分析结论,为避免非本征噪声干扰,提出了石墨烯本征背景1/f噪声规范性测量方案,为厘清和揭示石墨烯1/f噪声机制及特性探索可行技术途径.

A unified drain current 1/f noise model for GaN-based high electron mobility transistors

In this work, we present a theoretical and experimental study on the drain current 1/f noise in the AIGaN/GaN high electron mobility transistor （HEMT）. Based on both mobility fluctuation and carrier number fluctuation in a two- dimensional electron gas （2DEG） channel of AlGaN/GaN HEMT, a unified drain current 1/f noise model containing a piezoelectric polarization effect and hot carrier effect is built. The drain current 1/f noise induced by the piezoelectric polarization effect is distinguished from that induced by the hot carrier effect through experiments and simulations. The simulation results are in good agreement with the experimental results. Experiments show that after hot carrier injection, the drain current 1/f noise increases four orders of magnitude and the electrical parameter degradation Agm/gm reaches 54.9%. The drain current 1/f noise degradation induced by the piezoelectric effect reaches one order of magnitude; the electrical parameter degradation Agm/gm is 11.8%. This indicates that drain current 1/f noise of the GaN-based HEMT device is sensitive to the hot carrier effect and piezoelectric effect. This study provides a useful reliability characterization tool for the A1GaN/GaN HEMTs.

The 1/f noise in multiwalled carbon nanotubes

The 1/f noise in multiwalled carbon nanotubes bundles has been investigated between the frequency range of 0.1 to 30 Hz. At room temperature the noise spectrum is standard 1/f, and its level is proportional to the square of the bias voltage. With decreasing temperature the noise level also decreases. At 4.2 K the noise level follows a non-monotonic dependence against the bias voltage, showing a peak at a certain bias voltage, meanwhile its frequency dependence also deviates from the 1/f trend. This anomalous behaviour is discussed within the picture of environmental quantum fluctuation of charge transport in the samples.

THE WAVELET TRANSFORM BASED PROCESSING MEANS FOR 1/f NOISE IN MILLIMETER WAVE FOCAL PLANE ARRAY

After briefly introducing the characteristics of 1/f noise in millimeter wave focalplane array detectors, the paper analyses the relation of wavelet transform and 1/f noise in detail, suggests the fashion of decorrelating 1/f noise using the wavelet transform and deduces the relative expressions. The results of computer simulation show good effectiveness.

Low frequency noise in asymmetric double barrier magnetic tunnel junctions with a top thin MgO layer

Low frequency noise has been investigated at room temperature for asymmetric double barrier magnetic tunnel junctions（DBMTJs）, where the coupling between the top and middle CoFeB layers is antiferromagnetic with a 0.8-nm thin top Mg O barrier of the CoFeB/MgO/CoFe/CoFeB/MgO/CoFe B DBMTJ. At enough large bias, 1/f noise dominates the voltage noise power spectra in the low frequency region, and is conventionally characterized by the Hooge parameter αmag.With increasing external field, the top and bottom ferromagnetic layers are aligned by the field, and then the middle free layer rotates from antiparallel state（antiferromagnetic coupling between top and middle ferromagnetic layers） to parallel state. In this rotation process αmag and magnetoresistance-sensitivity-product show a linear dependence, consistent with the fluctuation dissipation relation. With the magnetic field applied at different angles（θ） to the easy axis of the free layer,the linear dependence persists while the intercept of the linear fit satisfies a cos（θ） dependence, similar to that for the magnetoresistance, suggesting intrinsic relation between magnetic losses and magnetoresistance.

AC800F系统在宣钢3#高炉的应用

宣钢3#高炉是1989年建成的1260立方米高炉,2003年扩容到1350立方米2010年大修将其扩容至2000立方米,自动控制系统将原来的infi90系统替换为ABB公司的AC800F系统。AC800F作为本工程控制核心的DCS 系统,将对整个高炉系统运行的过程数据进行采集、监视和控制。因此,要求其能长期稳定可靠运行。

PBTI stress-induced 1/f noise in n-channel FinFET

The influence of positive bias temperature instability(PBTI)on 1/f noise performance is systematically investigated on n-channel fin field-effect transistor(FinFET).The FinFET with long and short channel(L=240 nm,16 nm respectively)is characterized under PBTI stress from 0 s to 104 s.The 1/f noise features are analyzed by using the unified physical model taking into account the contributions from the carrier number and channel mobility fluctuations.The I d-V g,I d-V d,I g-V g tests are conducted to support and verify the physical analysis in the PBTI process.It is found that the influence of the channel mobility fluctuations may not be neglected.Due to the mobility degradation in a short-channel device,the noise level of the short channel device also degrades.Trapping and trap generation regimes of PBTI occur in high-k layer and are identified based on the results obtained for the gate leakage current and 1/f noise.

基于F⁃J法微动探测的表层结构调查

三维地震勘探常常处于城镇、道路等无法实施微测井等静校正方法的区域,近期人们尝试利用微动调查替代现有的静校正方法,取得了一定效果。现今微动调查在石油勘探的应用中主要通过提取面波频散曲线反演地层速度结构。该方法在石油勘探领域仍处于起步阶段,作为核心技术的频散成像方法种类繁多,其中2019年提出的频率—贝塞尔变换法(Frequency‑Bessel,F‑J)受到人们的广泛关注。相比空间自相关方法(SPAC),F‑J方法在利用背景噪声高阶模式面波成像上具有巨大优势。为了更好地研究F‑J方法的适用性,首先利用合成数据分析了不同观测系统和采集参数对F‑J成像的影响;然后利用四川某地实际噪声数据分析了不同观测系统、采集时间对F‑J频散成像的影响。实际应用中采用分段择优叠加得到的频散谱,可有效提高频散谱成像质量,为准确提取频散曲线提供了数据基础。进一步对比测井数据,发现利用基阶、高阶模式频散曲线进行多模式联合反演可精确地反演地层结构,使经济、高效地获得表层结构成为可能。

EMD结合多相正交矩阵及f检验的光谱信号去噪方法研究

由于受环境、仪器、人为因素的影响,光谱信号测量中往往存在噪声,会直接影响信号的分析结果。为了获得有效的光谱信号,文章提出一种经验模态分解(Empirical Mode Decomposition,EMD)结合多相正交矩阵及f检验的光谱信号去噪方法。该方法首先对加噪信号进行EMD分解,得到各固有模态函数(Intrinsic Mode Functions,IMF)后和多相正交矩阵相乘以降低信号的非周期自相关值,再通过f检验找到最佳分割点去除IMF分量的高频成分,乘逆矩阵去除噪声。仿真结果表明,原始信号经过EMD和多相正交矩阵结合处理后变成了复信号,成功实现了信号和噪声的有效分离,为后续光谱信号的处理研究奠定了基础。

f-x域去噪方法研究

本文提出一种拟线性化变换的方法 ,将地震数据进行拟线性变换 ,在此基础上进行 f - x域预测去噪 ,具体步骤为 :1利用正交多项式逼近技术 ,采用最大相似系数准则 ,计算出描述地震同相轴走势的相关系数 ;2利用相关系数对地震数据在空间上做拟线性化变换 ,对变换后的地震数据进行奇异滤波和 f - x域有效信号预测 ;3对预测结果进行反变换。理论数据试算和实际资料处理表明 ,本文提出的去噪方法具有去噪能力强、振幅保真性好、不降低纵向分辨率等特点 。

光电耦合器件1/f噪声和g-r噪声的机理研究

对光电耦合器件1/f噪声和gr噪声(产生-复合噪声)的偏置特性及其产生机理进行了实验和理论研究.结果表明在低频段,光电耦合器件的gr噪声通常表现为叠加1/f噪声,且两者均随输入电流的增加呈现先增大后减小的规律.通过测量前级噪声和后级噪声,发现光电耦合器件的gr噪声源为后级光敏三极管.理论分析表明光电耦合器件的1/f噪声主要为表面1/f噪声,gr噪声则源于光敏三极管发射结空间电荷区的深能级对载流子的俘获和发射.

f-x域算子外推去噪技术研究

在对f-x域预测滤波去噪技术深入研究的基础上，本文提出产工域算子外推去噪技术。f-x域算子外推去噪技术的假设前提和数学原理与f-x域预测滤波去噪技术大致相同。不同之处是它利用了有效反射信号和线性（或近似线性）干扰波的道间时差及能量的差异，以及有效信号同相轴的所有频率成分具有相同时差的假设条件，运用信噪比较高的中频段频率成分外推来求取高、低频带的预测算子。利用求得的预测算子进行预测滤波去噪处理，可使掺杂在有效地震反射数据中的随机噪声和线性（或近似线性）干扰波同时得到压制，同时还能使有效信号的高频成分得到较好的保护。

分形分析1/f噪声性能

电子器件的低频噪声通常由闪烁(1/f噪声)噪声、g-r噪声和爆裂噪声3种成分构成。这些噪声通常与晶体管表面状态或内部缺陷有关,其中,1/f噪声已成为对器件的质量评估及可靠性预测的重要指标。提出分形分析方法,对1/f噪声性能进行分析。仿真实验结果验证了该方法的可行性,为今后用分形理论研究器件低频噪声提供了理论依据。

MEMS压电矢量水听器低噪声前置放大电路

等效自噪声是微机电系统(MEMS)压电矢量水听器重要的性能指标,前置放大电路的噪声是其主要来源之一。为降低MEMS压电矢量水听器的自噪声,设计了一种低噪声前置放大电路。采用双JFET并联电路结构,辅以合适的偏置电路,对不同噪声源进行理论分析,优化电路参数,最终实现了噪声性能较优的低噪声前置放大电路的设计与制备。测试结果表明,在MEMS压电矢量水听器的工作频带内,低噪声前置放大电路信号放大无失真,电压增益为43.8d B,等效输入噪声电压谱密度为0.7nV√Hz@1 kHz其噪声性能较国内外同类型的放大电路具有一定优势。