To improve the feature extraction of ship-radiated noise in a complex ocean environment, fluctuation-based dispersion entropy is used to extract the features of ten types of ship-radiated noise. Since fluctuation-based dispersion entropy only analyzes the ship-radiated noise signal in single scale and it cannot distinguish different types of ship-radiated noise effectively, a new method of ship-radiated noise feature extraction is proposed based on fluctuation-based dispersion entropy (FDispEn) and intrinsic time-scale decomposition (ITD). Firstly, ten types of ship-radiated noise signals are decomposed into a series of proper rotation components (PRCs) by ITD, and the FDispEn of each PRC is calculated. Then, the correlation between each PRC and the original signal are calculated, and the FDispEn of each PRC is analyzed to select the Max-relative PRC fluctuation-based dispersion entropy as the feature parameter. Finally, by comparing the Max-relative PRC fluctuation-based dispersion entropy of a certain number of the above ten types of ship-radiated noise signals with FDispEn, it is discovered that the Max-relative PRC fluctuation-based dispersion entropy is at the same level for similar ship-radiated noise, but is distinct for different types of ship-radiated noise. The Max-relative PRC fluctuation-based dispersion entropy as the feature vector is sent into the support vector machine (SVM) classifier to classify and recognize ten types of ship-radiated noise. The experimental results demonstrate that the recognition rate of the proposed method reaches 95.8763%. Consequently, the proposed method can effectively achieve the classification of ship-radiated noise.
Various nanovesicles loaded with tumor-associated antigens (TAAs) have been developed for melanoma treatment. However, the slow release of antigens leads to an ineffective immune response. pH-responsive gatekeepers have been reported for achieving "zero release", but the complicated synthesis process limits their applications. Therefore, it is essential to develop a simple and easy-to-synthesize gatekeeper for the controlled release of proteins. In our work, mesoporous silica nanoparticles (MSNs) were used for model vaccine ovalbumin (OVA) loading. Metal− organic frameworks (MOFs) with pH-responsive ability were synthesized as gatekeepers via a one-step method, coordinating Eu ions with guanine monophosphate (GMP) on the MSN surface. CpG oligodeoxynucleotides were used as TLR9 agonists, which could specifically bind to the MSN-OVA@MOF surface through Watson−Crick base pairing for further promoting immune responses. Our work has demonstrated that MOF-coated MSN could be effectively co-loaded with OVA and CpG (MSN-OVA@MOF@CpG) and present antigens to antigen-presenting cells. The coated MOF, as gatekeepers, can be degraded in endo/lysosomes and release OVA and CpG, which then induces more vital OVA-specific T cell responses for high-efficient inhibition of melanoma cancer growth and metastasis.
Objective: Normal pregnancy is associated with profound alterations in the maternal cardiovascular system and PPG represents a sensitive and convenient technique capable of tracking changes in the pulsatile function of arteries. The aim of this study was to investigate the effects of maternal cardiovascular alterations on the finger tip photoplethysmography (PPG) during normal gestation. Methods: Thirty five healthy pregnant women were studied at each trimester of pregnancy and again on gestational age using PPG signals, peripheral blood pressure (BP) and heart rate (HR). Results: Comparing with nonpregnant controls, several characteristic differences in PPG derived parameters and morphologies occurred in the pregnant. PAI, RI, PTT as well as AUC1 and Y1 of bcAUC1 were different and significant difference had been found in second and third trimester, despite little change in the peripheral blood pressure. The mean heart rate increased linearly with gestational age. Conclusion: This study has confirmed that normal pregnancy is associated with profound alterations in PPG signals occurred principally as a result of maternal cardiovascular adaptation and PPG-based noninvasive assessment of cardiovascular activities is feasible throughout pregnancy. Using this technique we demonstrated a delay in wave reflection within the arterial tree and a reduction in magnitude of arterial wave reflections in normal pregnancy which is consistent with previous observations and the known cardiovascular changes of pregnancy.
In order to improve the fabrication efficiency and performance of an ultrasonic transducer (UT), a particle swarm optimization (PSO) algorithm-based design method was established and combined with an electrically equivalent circuit model. The relationship between the design and performance parameters of the UT is described by an electrically equivalent circuit model. Optimality criteria were established according to the desired performance; then, the design parameters were iteratively optimized using a PSO algorithm. The Pb(ZrxTi1−x)O3 (PZT) ceramic UT was designed by the proposed method to verify its effectiveness. A center frequency of 6 MHz and a bandwidth of −6 dB (70%) were the desired performance characteristics. The optimized thicknesses of the piezoelectric and matching layers were 255 μm and 102 μm. The experimental results agree with those determined by the equivalent circuit model, and the center frequency and −6 dB bandwidth of the fabricated UT were 6.3 MHz and 68.25%, respectively, which verifies the effectiveness of the developed optimization design method.
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