A Sorting Method of SAR Emitter Signal Sorting Based on Self-Supervised Clustering

Most existing methods for sorting synthetic aperture radar (SAR) emitter signals rely on either unsupervised clustering or supervised classification methods. However, unsupervised clustering can consume a significant amount of computational and storage space and is sensitive to the setting of hyperparameters, while supervised classification requires a considerable number of labeled samples. To address these limitations, we propose a self-supervised clustering-based method for sorting SAR radiation source signals. The method uses a constructed affinity propagation-convolutional neural network (AP-CNN) to perform self-supervised clustering of a large number of unlabeled signal time-frequency images into multiple clusters in the first stage. Subsequently, it uses a self-organizing map (SOM) network combined with inter-pulse parameters for further sorting in the second stage. The simulation results demonstrate that the proposed method outperforms other depth models and conventional methods in the environment where Gaussian white noise affects the signal. The experiments conducted using measured data also show the superiority of the proposed method in this paper

Simple and Excellent Selective Chemiluminescence-Based CS₂ On-Line Detection System for Rapid Analysis of Sulfur-Containing Compounds in Complex Samples

To study the interesting chemical reaction phenomenon can greatly contribute to the development of an innovative analytical method. In this paper, a simple CL reaction cell was constructed to study the chemiluminescence (CL) emission from the thermal oxidation of carbon disulfide (CS₂). We found that the CL detection of CS₂ exhibits unique characteristics of excellent selectivity and rapid response capacity. Experimental investigations together with theoretical calculation were performed to study the mechanism behind the CL reaction. The results revealed that the main luminous intermediates generated during the thermal degradation of CS₂ are SO₂* and CO₂*. Significantly, this CL emission phenomenon has a wide application due to many sulfur-containing compounds that can convert to CS₂ under special conditions. On the basis of this scheme, a CS₂-generating and detection system was developed for rapid measurement of CS₂ or other compounds that can convert to CS₂. The usefulness of the system was demonstrated by measuring dithiocarbamate (DTC) pesticides (selected mancozeb as a representative analyte) based on the evolution of CS₂ in spiked agricultural products. Results showed that the system allows online and large volume detection of CS₂ under nonequilibrium condition, which greatly reduces the analytical time. The concentrations of mancozeb in the spiked samples were well-quantified with satisfied recoveries of 76.9–97.3%. The system not only addresses the urgent need for rapid in-field screening of DTC residues in foodstuffs but also opens a new opportunity for the fast, convenient, and cost-effective detection of CS₂ and some other sulfur-containing compounds in complex samples

Development of a Cyclic System for Chemiluminescence Detection

In this paper, we described a new concept of cyclic chemiluminescence (CCL) detection, and a homemade system was designed to realize such detection. The direction of the carrier in the CCL system is in a state of periodical change that can trigger a succession of chemiluminescence (CL) reactions in a single sample injection. Therefore, in contrast to the traditional CL detection, which only records a single signal, CCL allows us to obtain multistage signals. To evaluate the new method, the cataluminescence (CTL) reaction of the volatile organic compounds (VOCs) on a nanosized catalyst was selected as the analytical model. We found that each CCL reaction has a unique exponential decay equation (EDE) to describe the change law of its multistage signals. Further study showed that the initial amount (<i>A</i>) of the EDE is linear with the analyte concentration, while the decay coefficient (<i>k</i>) is a characteristic constant for a given reaction. The formation mechanism of the exponential function and the determinants of the decay coefficient were discussed in detail. As a distinct application, CCL is capable of rapidly discriminating various analytes and even structural isomers

Development of a Simple Cataluminescence Sensor System for Detecting and Discriminating Volatile Organic Compounds at Different Concentrations

The detection and identification of volatile organic compounds (VOCs) is one of the most serious subjects in the field of chemical sensing, but it remains an enormous challenge. Usually, during the sensing of gases involved in chemical reactions, the residual gas of that reaction (including undecomposed analytes and reaction products) are considered waste gases and released into the air. Here, a novel cataluminescence (CTL) sensing method based on detection of the luminescent intensities of both the analyte (<i>I</i>_A) and its products (<i>I</i>_R) was developed and used to identify VOCs at different concentrations. After the analyte gas passed through the first sensing material, the product gas was treated as a new reactant and passed through the second sensing material (which could be the same as or different from the first material). The luminescent signals of <i>I</i>_A and <i>I</i>_R were recorded over a short period of time using one photomultiplier. We found the ratio of <i>I</i>_A to <i>I</i>_R (<i>I</i>_A/<i>I</i>_R) to be a unique characteristic of a given analyte within a wide range of concentrations. To illustrate the new method, 11 kinds of organic gases were successfully identified using <i>I</i>_A/<i>I</i>_R values. The most distinct feature of this method is that it allows the user to obtain many more luminescent signals from the sensing materials than common methods. It does so by allowing different flow channels of the analyte gas. This simple method here was used to discriminate different species, homologous series, and isomers in different concentrations. This method could be applied to chemical sensing arrays to increase the discrimination ability or decrease the number of sensing units required

Noninvasive Strategy Based on Real-Time in Vivo Cataluminescence Monitoring for Clinical Breath Analysis

The development of noninvasive methods for real-time in vivo analysis is of great significant, which provides powerful tools for medical research and clinical diagnosis. In the present work, we described a new strategy based on cataluminescence (CTL) for real-time in vivo clinical breath analysis. To illustrate such strategy, a homemade real-time CTL monitoring system characterized by coupling an online sampling device with a CTL sensor for sevoflurane (SVF) was designed, and a real-time in vivo method for the monitoring of SVF in exhaled breath was proposed. The accuracy of the method was evaluated by analyzing the real exhaled breath samples, and the results were compared with those obtained by GC/MS. The measured data obtained by the two methods were in good agreement. Subsequently, the method was applied to real-time monitoring of SVF in exhaled breath from rat models of the control group to investigate elimination pharmacokinetics. In order to further probe the potential of the method for clinical application, the elimination pharmacokinetics of SVF from rat models of control group, liver fibrosis group alcohol liver group, and nonalcoholic fatty liver group were monitored by the method. The raw data of pharmacokinetics of different groups were normalized and subsequently subjected to linear discriminant analysis (LDA). These data were transformed to canonical scores which were visualized as well-clustered with the classification accuracy of 100%, and the overall accuracy of leave-one-out cross-validation procedure is 88%, thereby indicating the utility of the potential of the method for liver disease diagnosis. Our strategy undoubtedly opens up a new door for real-time clinical analysis in a pain-free and noninvasive way and also guides a promising development direction for CTL

A New Method for Identifying Compounds by Luminescent Response Profiles on a Cataluminescence Based Sensor

Rapid identification of different compounds has been proven to be one of the most dynamic fields in analytical chemistry. Herein, a very simple cataluminescence-sensor-based (CTL-based) method suitable for rapid identification of compounds is reported. The oxidation of analytes was catalyzed in a closed reaction cell (CRC) containing enough air to facilitate complete luminescent response profiles with several peaks. The multipeaked response profiles are characteristic of analytes and can be used for identifying compounds. In existing CTL-based sensors, CTL reactions take place in an airstream flow reaction cell (AFRC) in which a continuous airstream carries the analytes flow across the catalyst’s surface. The luminescent response profiles obtained are transitory and lack characteristic features, so they cannot be used to identify different compounds. To illustrate the new method, 12 medicines and 4 organic gases were examined in CRC sensors. Results showed that these compounds could be successfully identified through their unique luminescent response profiles. The response was rapid and the system was inexpensive and easy to handle. We believe that it has great potential for real-world use

Tribological properties of (Ti, Al)N films with different Al/Ti atomic ratios deposited by magnetron sputtering

Magnetron sputtering was used to deposit (Ti, Al)N films with different Al/Ti atomic ratios by changing the current of the Al target and to study their tribological properties. The phase composition, microstructure and elemental distribution of films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). The influence of the ratio between Al and Ti atoms on the tribological properties and the mechanical properties of the films was analyzed. The conclusions showed that there was a tendency for films to shift from the crystalline to the amorphous state as the Al/Ti atomic ratio increases. Herein, changes in film microhardness were related to the substitution relationship between Ti atoms and Al atoms. Especially, when the Al/Ti atomic ratio was 0.54, coefficient of friction (COF) and specific wear rate were the lowest. Compared with TiN film, (Ti, Al)N films have higher microhardness due to the solid solution hardening caused by the substitution between Al and Ti atoms to produce lattice distortion. These factors make films have excellent tribology performance

Liquid-Phase Cyclic Chemiluminescence for the Identification of Cobalt Speciation

Accurate discrimination of metal species is a significant analytical challenge. Herein, we propose a novel methodology based on liquid-phase cyclic chemiluminescence (CCL) for the identification of cobalt speciation. The CCL multistage signals (In) of the luminol–H2O2 reaction catalyzed by different cobalt species have different decay coefficients k. Thereby, we can facilely identify various cobalt species according to the distinguishable k values, including the complicated and structurally similar cobalt complexes, such as analogues of [Co­(NH3)5X]n+ (X = Cl–, H2O, and NH3), Co­(II) porphyrins, and bis­(2,4-pentanedione) cobalt­(II) derivatives. Especially, the number of substituent atoms also influences the k value greatly, which allows excellent discrimination between complexes that only have a subtle difference in the substituent group. In addition, linear discriminant analysis based on In provides a complementary solution to improve the differentiating ability. We performed density functional theory calculations to investigate the interaction mode of H2O2 over cobalt species. A close negative correlation between the adsorption energy and the k value is observed. Moreover, the calculation of energy evolutions of H2O2 decomposition into a double hydroxide radical shows that a high level of consistency exists between the activation energy barrier and the k value. The results further demonstrate that the decay coefficient of the CCL multistage signal is associated with the catalytic reactivity of the cobalt species. Our work not only broadens the application of chemiluminescence but also provides a complementary technology for speciation analysis