A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

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The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis

A new Ensemble Empirical Mode Decomposition (EEMD) is presented. This new approach consists of sifting an ensemble of white noise-added signal (data) and treats the mean as the final true result. Finite, not infinitesimal, amplitude white noise is necessary to force the ensemble to exhaust all possible solutions in the sifting process, thus making the different scale signals to collate in the proper intrinsic mode functions (IMF) dictated by the dyadic filter banks. As EEMD is a time–space analysis method, the added white noise is averaged out with sufficient number of trials; the only persistent part that survives the averaging process is the component of the signal (original data), which is then treated as the true and more physical meaningful answer. The effect of the added white noise is to provide a uniform reference frame in the time–frequency space; therefore, the added noise collates the portion of the signal of comparable scale in one IMF. With this ensemble mean, one can separate scales naturall...

/pdf/ensemble-empirical-mode-decomposition-a-noise-assisted-data-4htvj7tcuy.pdf

Ensemble empirical mode decomposition: a noise-assisted data analysis method

During the late 1990s, Huang introduced the algorithm called Empirical Mode Decomposition, which is widely used today to recursively decompose a signal into different modes of unknown but separate spectral bands. EMD is known for limitations like sensitivity to noise and sampling. These limitations could only partially be addressed by more mathematical attempts to this decomposition problem, like synchrosqueezing, empirical wavelets or recursive variational decomposition. Here, we propose an entirely non-recursive variational mode decomposition model, where the modes are extracted concurrently. The model looks for an ensemble of modes and their respective center frequencies, such that the modes collectively reproduce the input signal, while each being smooth after demodulation into baseband. In Fourier domain, this corresponds to a narrow-band prior. We show important relations to Wiener filter denoising. Indeed, the proposed method is a generalization of the classic Wiener filter into multiple, adaptive bands. Our model provides a solution to the decomposition problem that is theoretically well founded and still easy to understand. The variational model is efficiently optimized using an alternating direction method of multipliers approach. Preliminary results show attractive performance with respect to existing mode decomposition models. In particular, our proposed model is much more robust to sampling and noise. Finally, we show promising practical decomposition results on a series of artificial and real data.

Variational Mode Decomposition

One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic...

/pdf/accumulation-and-fragmentation-of-plastic-debris-in-global-2ayi1pcd8z.pdf

Accumulation and fragmentation of plastic debris in global environments.

Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

Satellite observations of sub-mesoscale vortex trains in the western boundary of the South China Sea

[1] A merged scatterometer wind data set from ERS-1/2, NSCAT, and QuikSCAT missions was used to observe the atmospheric convergence zones (ACZs) caused by the western boundary currents, the Gulf Stream and Kuroshio. The long-term means of the atmospheric convergence show the ACZs' spatial features, which are related to the precipitation patterns in these regions. Seasonal images of the ACZs were produced to show annual cycles of the ACZs, indicating that the intensities of the ACZs over these two regions strengthen in winter and weaken in summer. Furthermore, we calculated the total convergence over the Gulf Stream and Kuroshio ACZs, which is defined as the integral of the convergence over the ACZs. The interannual variability of the total convergence was extracted by using a multi-stage filter, revealing that in response to strong El Nino events in 1991–92 and 1997–98, the total convergence reached maxima.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002GL015015

Observation of western boundary current atmospheric convergence zones using scatterometer winds

Tide-Induced Periodic Sea Surface Temperature Drops in the Coral Reef Area of Nanwan Bay, Southern Taiwan

A method is presented for estimating the amplitudes of internal waves (IWs) in ocean colour imagery. The method is tested in the northern South China Sea (SCS) because the environmental conditions there are such that IWs are generated frequently and can therefore be observed easily. A relationship between satellite-derived chlorophyll concentration (chl) and the amplitudes of IWs is obtained. Using a deep chlorophyll maximum (DCM) model, the amplitude at the light penetration depth can be estimated. From theoretical models, the amplitude of an IW at the depth where the maximum vertical isopycnal displacement appears is also derived. The results indicate that the amplitudes of IWs in the northern SCS determined by the methods developed in this study are comparable with historical regional data.

Estimating amplitudes of internal waves using satellite ocean colour imagery of the South China Sea

Objective Many studies have revealed that long non-coding RNAs (lncRNAs) are related to various cancers, including colorectal cancer (CRC). This study aims to explore the biological function of lncRNA PSMA3-AS1 in CRC progression. Materials and methods The expression levels of PSMA3-AS1 and miR-4429 were assessed by RT-qPCR. CRC progression was explored by cell viability, migration, and invasion using CCK-8 and transwell assays. The interaction between PSMA3-AS1 and miR-4429 was verified by bioinformatics analysis, Dual-Luciferase assay, and RIP assay. Results It was found that PSMA3-AS1 expression was increased and miR-4429 expression was decreased in CRC tissues and cells. In addition, PSMA3-AS1 interference markedly hindered the proliferation, migration, and invasion of CRC cells. MiR-4429 was a direct target of PSMA3-AS1, and the knockdown of PSMA3-AS1 significantly suppressed miR-4429 expression. The depletion of PSMA3-AS1 inhibited CRC progression, which was neutralized by miR-4429 inhibitor. Conclusions PSMA3-AS1 accelerated CRC progression by regulating miR-4429 expression, which could be used as a potential therapeutic target for CRC patients.

Quanan Zheng

Papers

Satellite observations of sub-mesoscale vortex trains in the western boundary of the South China Sea

Observation of western boundary current atmospheric convergence zones using scatterometer winds

Tide-Induced Periodic Sea Surface Temperature Drops in the Coral Reef Area of Nanwan Bay, Southern Taiwan

Estimating amplitudes of internal waves using satellite ocean colour imagery of the South China Sea

LncRNA PSMA3-AS1 promotes colorectal cancer cell migration and invasion via regulating miR-4429.