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Youpei Zhang Limin Zhang Lixi Wen 《Journal of Mathematical Analysis and Applications》2021,493(2):124535
We are concerned with qualitative analysis of weak solutions for a class of magnetic Laplace equations with lack of compactness. By variational arguments, we establish related nonexistence, existence and multiplicity results. 相似文献
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The trend prediction of the stock is a main challenge. Accidental factors often lead to short-term sharp fluctuations in stock markets, deviating from the original normal trend. The short-term fluctuation of stock price has high noise, which is not conducive to the prediction of stock trends. Therefore, we used discrete wavelet transform (DWT)-based denoising to denoise stock data. Denoising the stock data assisted us to eliminate the influences of short-term random events on the continuous trend of the stock. The denoised data showed more stable trend characteristics and smoothness. Extreme learning machine (ELM) is one of the effective training algorithms for fully connected single-hidden-layer feedforward neural networks (SLFNs), which possesses the advantages of fast convergence, unique results, and it does not converge to a local minimum. Therefore, this paper proposed a combination of ELM- and DWT-based denoising to predict the trend of stocks. The proposed method was used to predict the trend of 400 stocks in China. The prediction results of the proposed method are a good proof of the efficacy of DWT-based denoising for stock trends, and showed an excellent performance compared to 12 machine learning algorithms (e.g., recurrent neural network (RNN) and long short-term memory (LSTM)). 相似文献
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Tomohiro Sakata Shingo Ogawa Keiko Inoue Yumiko Shimizu Yusaku Tanahashi 《Surface and interface analysis : SIA》2022,54(6):661-666
To systematically evaluate the quality of SiNx films in multi-stacked structures, we investigated the effects of post-deposition annealing (PDA) on the film properties of SiNx within the SiO2/SiNx/SiO2/Si stacked structure by performing X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), Fourier transform infrared (FT-IR) spectroscopy, and scanning transmission electron microscope–electron energy loss spectroscopy (STEM-EELS) analyses. The XPS results showed that PDA induces the oxidation of the SiNx layer. In particular, new finding is that Si-rich SiNx in the SiNx layer is preferentially oxidized by PDA even in multi-stacked structure. The XRR results showed that the SiNx layer becomes thinner, whereas the interface layer between the SiNx layer and Si becomes thicker. It is concluded by STEM-EELS and XPS that this interface layer is SiON layer. The density of N–H and Si–H bonding within the stacked structure strongly depends on the PDA temperature. Our study helps elucidate the properties of SiNx films in stacked structures from various perspectives. 相似文献
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针对大白菜农药残留传统化学检测手段存在前期处理过程繁琐、检测周期长等不足,提出了一种快速无损识别大白菜农药残留种类的方法。以1组无农药残留和4组含有均匀喷洒农药(毒死蜱、乐果、灭多威和氯氰菊酯)的大白菜样本为研究对象(药液浓度配比分别为0.10,1.00,0.20和2.00 mg·kg-1),经12小时自然吸收后,利用高光谱成像系统获取400~1 000 nm高光谱图像,并选取ROI感兴趣区域后经多元散射校正(MSC)预处理;分别采用竞争性自适应重加权算法(CARS)、主成分分析算法(PCA)和离散小波变换(DWT)降维(分别基于db1,sym2,coif1,bior2.2和rbio1.5小波基函数);最后,将降维后的高光谱数据分别输入卷积神经网络(CNN)、多层感知机(MLP)、K最邻近算法(KNN)和支持向量机(SVM)建立模型并比较。结果显示,CNN,MLP,KNN和SVM算法均在降维算法DWT(小波基函数及变换层数分别为coif1-2,coif1-4,bior2.2-2和sym2-2)取得最优总体精度分别为91.20%,83.20%,66.40%和90.40%,Kappa系数分别为0.89,0.79,0.58和0.88,预测集用时分别为86.01,63.23,20.02和14.03 ms,总体精度和Kappa指标均优于基于CARS和PCA降维算法建模结果。可见,高光谱与离散小波变换和卷积神经网络相融合显著提高分类识别精度,改善“休斯”现象,为实现无损和快速检测识别大白菜农残提供一个新的方法。 相似文献
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当初值不光滑时,时间分数阶齐次扩散方程数值方法的精度会下降.为了得到高阶时间收敛格式,提出加权移位的Grünwald-Letnikov的修正格式,运用Lubich的修正方法,得到非光滑时间分数阶齐次扩散方程的收敛阶仍为O(k2).最后,通过数值算例验证了数值计算结果与理论计算结果一致. 相似文献
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Wei Gao Pundikala Veeresha Doddabhadrappla Gowda Prakasha Haci Mehmet Baskonus 《Numerical Methods for Partial Differential Equations》2021,37(1):210-243
The pivotal aim of the present work is to find the numerical solution for fractional Benney–Lin equation by using two efficient methods, called q ‐homotopy analysis transform method and fractional natural decomposition method. The considered equation exemplifies the long waves on the liquid films. Projected methods are distinct with solution procedure and they are modified with different transform algorithms. To illustrate the reliability and applicability of the considered solution procedures we consider eight special cases with different initial conditions. The fractional operator is considered in Caputo sense. The achieved results are drowned through two and three‐dimensional plots for different Brownian motions and classical order. The numerical simulations are presented to ensure the efficiency of considered techniques. The behavior of the obtained results for distinct fractional order is captured in the present framework. The outcomes of the present investigation show that, the considered schemes are efficient and powerful to solve nonlinear differential equations arise in science and technology. 相似文献