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.

Study the Effect of Thickness on the Performance of PM6:Y6 Organic Solar Using SCAPS Simulation

In this study, organic solar cells (OSCs) with an active layer, a blend of polymer of non-fullerene (NFA) Y6 as an acceptor, and donor PBDB-T-2F as donor were simulated through the one-dimensional solar capacitance simulator (SCAPS-1D) software to examine the performance of this type of organic polymer thin-film solar cell by varying the thickness of the active layer. PFN-Br interfacial layer entrenched in OPV devices gives overall enhanced open-circuit voltage, short-circuit current density and fill factor thus improving device performance. PEDOT: PSS is an electro-conductive polymer solution that has been extensively utilized in solar cell devices as a hole transport layer (HTL) due to its strong hole affinity, good thermal and mechanical stability, high work function, and high transparency in the visible range. The structure of the organic solar cell is ITO/PEDOT: PSS/BTP-4F: PBDB-T-2F/PFN-Br/Ag. Firstly, the active layer thickness was optimized to 100 nm;after that, the active-layer thickness was varied up to 900 nm. The results of these simulations demonstrated that the active layer thickness improves efficiency significantly up to 500 nm, then it decreased with increasing the thickness of the active layer from 600 nm, also notice that the short circuit current and the fill factor decrease with increasing the active layer from 600 nm, while the open voltage circuit increased with increasing the thickness of the active layer. The optimum thickness is 500 nm.

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 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.

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.

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.

基于Y系数法的频谱分析仪噪声系数测量

噪声系数是反映射频模块内部噪声的重要指标,射频模块设计及选型都离不开对噪声系数的测量,因此,一般使用噪声系数分析仪进行测试。由于并非每个实验室都配备有相关仪器,因此,相比噪声系数分析仪,频谱分析仪的配备较普遍。本文以Y系数法测量噪声系数的原理,通过软件设计,实现了频谱分析仪可替代噪声系数分析仪,并进行噪声系数测量。

基于ICEEMDAN和分布熵的SS-Y伸缩仪信号随机噪声压制方法

结合改进的自适应噪声完备集合经验模态分解(ICEEMDAN)与分布熵(DistEn),提出一种无需自定义算法参数、去噪效果较好的伸缩仪信号随机噪声压制方法。首先将伸缩仪信号进行ICEEMDAN处理,得到若干个本征模态函数(IMF);然后计算各IMF分量的分布熵值,根据不同分布熵值的大小和表征的分量信号混乱程度,有针对性地对各IMF进行取舍;最后进行线性重构。设计仿真信号去噪实验和SS-Y伸缩仪信号去噪实验,结果表明,基于ICEEMDAN-DistEn去噪模型的伸缩仪信号重构还原度较好,去噪效果显著,明显优于CEEMDAN-DistEn、小波去噪和卡尔曼滤波等去噪模型。

Y因子法测量天线噪声温度的不确定性分析

介绍了Y因子法测量天线噪声温度的原理方法,分析了常温负载和低噪声放大器噪声温度的不确定性对天线噪声温度测量的影响,推导了天线噪声温度测量的绝对误差计算公式,研究了低噪声放大器噪声温度对天线噪声温度测量精度的影响,提出了改善天线噪声温度测量精度的方法。最后,给出了65 m射电望远镜天线L波段、C波段和X波段噪声温度测量结果。测量结果的误差分析表明:65 m射电望远镜天线噪声温度测量的绝对误差≤±2.48 K。

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.

基于Y型顶部结构优化的声屏障降噪设计

为提升声屏障在城市高架道路上的噪声控制性能,开展了基于Y型顶部结构的声屏障结构设计和性能优化。采用有限元仿真,计算了声屏障所在区域的近场和远场声场分布,对比了折臂型声屏障和Y型声屏障性能。近场声场仿真表明,Y型声屏障相较折臂型声屏障多了朝向道路外侧的折臂,故对距离声屏障较近的底部区域的噪声控制有明显的改善。选取典型的城市高架道路进行高架沿线建筑立面处的声场分布计算,结果表明,加装声屏障对交通道路沿线建筑具有较好的噪声遮挡作用,Y型声屏障可在折臂型声屏障的基础上,进一步将声级降低1~2dB。

F92钢Y型异径锻造三通焊接接头焊后热处理研究及实践

火力发电厂四大管道F92钢Y型异径锻造三通焊接接头焊后热处理是火电建设工程中技术要求较高的一类问题,尤其是锻造三通接管长度<100 mm的焊接接头。文中结合某1 000 MW二次再热机组一次高温再热蒸汽管道F92钢Y型异径锻造三通焊接接头焊后热处理,锻造三通接管长度为80 mm,通过采用Y型异径锻造三通的3个焊接接头同时焊后热处理的技术方案,热处理后焊缝及母材组织正常,焊缝、热影响区、管道和三通母材硬度符合标准要求;同时根据一次高温再热蒸汽管道F92钢Y型异径锻造三通焊接接头焊后热处理的成功实施,实现了主蒸汽、二次高温再热蒸汽管道F92钢Y型异径锻造三通焊接接头焊后热处理一次合格。Y型异径锻造三通3个焊接接头同时焊后热处理方案的成功应用,可为后续同类型部件的焊后热处理提供借鉴。

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.

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.

HET-Y(C)型沥青混凝土在提升隧道路面质量中的关键工艺研究

HET-Y(C)型半开级配沥青混凝土具有较大的孔隙及良好的抗滑能力,能够较好地吸收噪声,解决隧道水泥混凝土路面行车噪声大、抗滑性能衰减快、行车舒适性差等问题。文章依托实体工程进行研究,得到拌和时间、摊铺速度、碾压工艺等影响HET-Y(C)型沥青混凝土路面质量的关键施工参数。通车1年后,路面国际平整度指数约为1.0m/km,横向力系数大于62,等级均为优;100km/h行车速度下路面噪声小于73dB,极大提高了隧道路面的行车安全性及舒适性。

化合物CF_3IXY(X,Y=F,Cl,Br,I)成键特性的理论研究

用Gaussian98W程序在HF/STO-3G和B3LYP/6-31G(d)水平上对CF3IXY(X,Y=F,Cl,Br,I)类共10个化合物进行了全优化计算,并计算了它们的键能.对该类化合物的几何结构、成键特性、键能及性质间的关系进行了探讨,进而对该类化合物的反应性及合成其它该类化合物的可能性进行了预测.

f-x-y域最小平方反演预测滤波

在对f-x域预测滤波方法深入研究的基础上,本文提出了f-x-y域最小平方反演预测滤波方法。该去噪方法的基本思想是假设信号中也存在不可预测部分,利用信号中的不可预测部分和随机噪音的联合分布建立目标函数,进而实现频率空间的预测滤波。理论模型试算和实际资料处理表明,该方法较f-x-y域预测滤波能更好的提高地震资料的信噪比,保持地震同相轴的连续性。

稀土氟化物Y_(0.97)Er_(0.03)F_3纳米材料的制备及上转换发光

通过燃烧法和控温热反应法制备了稀土氟化物纳米材料,利用XRD和TEM对样品进行了分析和表征。测量了发射波长为980nm激光二极管激发下所得纳米材料的上转换发光性质。

基于奇异值分解的f-x-y域滤波方法

在简单回顾奇异值法压制随机噪音的基础上,提出了基于奇异值分解的f x y域滤波方法。该方法是一种三维去噪方法,它不需求取同相轴的倾角就可以去除倾斜同相轴的随机噪音,同时还可以较好地保持地震信号的振幅。经理论模型试算表明,该方法运算速度快,效果明显,是一种可行的去噪方法。