Intermittent flow is one of the most complex flow patterns in gas-liquid two-phase flow in pipelines. The leakage of pipeline intermittent flow poses a threat to the operating safety. In order to ...improve the application of acoustic method to gas-liquid two-phase leakage detection, the amplitude characteristics and propagation velocity of dynamic pressure wave of intermittent flow for gas-liquid two-phase pipeline leakage were investigated. Experiments with conditions of superficial liquid velocity (vsL) from 0.57 m/s to 1.06 m/s, superficial gas velocity (vsG) from 0.3 m/s to 4.47 m/s, leakage aperture from 4 mm to 9 mm were carried out, and the characteristics were studied by time-domain analysis, frequency-domain analysis and time-frequency analysis. The propagation velocity formula of dynamic pressure wave in two-phase medium was fitted based on Levenberg-Marquardt algorithm, and the propagation velocity of straight pipe and elbow pipe was discussed. The experimental results indicate that the peak-to-peak value of dynamic pressure wave measured by sensor within 4.25 m increases during top or mid sustained leakage when leak aperture is larger than 4 mm in elongated bubble flow and 6 mm in slug flow. The amplitude of sustained leakage dynamic pressure increases as gas flow rate increases. The low frequency energy of signal increases immediately when leakage occurs, the energy of signal mainly concentrates at 0–15 Hz, the frequency amplitude of sustained leakage signal is much higher than normal flow signal and leak occur signal. As the gas volume fraction β increases from 0.23 to 0.75, the dynamic pressure propagation velocity decreases from 33.13 m/s to 26.5 m/s and then increases from 26.5 m/s to 66.25 m/s. The propagation velocity increases when it flows through an elbow pipe section. The results are meaningful for further study of two-phase pipeline slug flow leakage detection and location.
•Experiments of gas-liquid two-phase intermittent flow leak-detection based dynamic pressure is carried out.•Time-frequency analysis of leakage signal is performed based on generalized S-transformation.•Velocity propagation formula is fitted based on Levenberg-Marquardt algorithm.•Detecting method and dynamic pressure sensor arrangement suggestion is given for leak-detection.
Pressurized liquefied natural gas (PLNG) is a new natural gas liquefaction solution proposed in recent years for reducing the construction and operating costs of floating liquefied natural gas ...(FLNG). For natural gas, the liquefaction temperature is strongly influenced by the pressure; when the pressure increases, the liquefaction temperature of natural gas increases accordingly. The increase in the liquefaction temperature of natural gas leads to a higher solubility of impurities such as carbon dioxide, which means that the pretreatment standards for liquefied natural gas can be reduced. Therefore, the use of PLNG technology can simplify pretreatment plants and significantly reduce construction and operating costs. In order to better apply PLNG technology to FLNG, it is necessary to understand the solubility of carbon dioxide in pressurized LNG and the phase change during liquefaction. To achieve this, experimental setups are needed to simulate the temperature and pressure environment of the LNG to obtain the relevant data and observe the relevant phenomena. After a literature research and analysis of the advantages and disadvantages of previous experimental setups, several improvements are proposed in this paper, and based on this, a visualization device is designed for studying the liquid–solid-phase equilibrium experiment of CO2 in PLNG. The device has a pressure resistance of 20 MPa, a minimum operating temperature of 77 K, and a variable volume function. It is also equipped with a sapphire window to be able to observe the inside of the device. In order to verify the superiority of the device, experiments were conducted using the device to verify the pressure resistance, variable volume, and visualization functions of the device. The experimental results show that the experimental device designed in this paper does have a certain superiority.
Owing to the complexity of the ocean background noise, underwater acoustic signal denoising is one of the hotspot problems in the field of underwater acoustic signal processing. In this paper, we ...propose a new technique for underwater acoustic signal denoising based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), mutual information (MI), permutation entropy (PE), and wavelet threshold denoising. CEEMDAN is an improved algorithm of empirical mode decomposition (EMD) and ensemble EMD (EEMD). First, CEEMDAN is employed to decompose noisy signals into many intrinsic mode functions (IMFs). IMFs can be divided into three parts: noise IMFs, noise-dominant IMFs, and real IMFs. Then, the noise IMFs can be identified on the basis of MIs of adjacent IMFs; the other two parts of IMFs can be distinguished based on the values of PE. Finally, noise IMFs were removed, and wavelet threshold denoising is applied to noise-dominant IMFs; we can obtain the final denoised signal by combining real IMFs and denoised noise-dominant IMFs. Simulation experiments were conducted by using simulated data, chaotic signals, and real underwater acoustic signals; the proposed denoising technique performs better than other existing denoising techniques, which is beneficial to the feature extraction of underwater acoustic signal.
Leak detection technology, based on the disturbance-reflected signal, can realize pipeline state inspection without relying on the transient characteristics of leakage. However, the lack of research ...on the factors affecting the detection effect of this method greatly restricts its popularization and application. Therefore, this paper realizes the valve opening and closing through dynamic mesh technology and further establishes a 2D pipeline disturbance and reflection signal detection model. The correctness of the computational fluid dynamics (CFD) model detection mechanism was verified by theoretical analysis and indoor pipe flow experiments. In this process, it was found that reflections from boundaries, such as the pipe end, could also be identified and did not interfere with leak-related signals. In addition, the positioning errors of the leakage hole and the pipe end were 4.447% and 0.121%, respectively, and accurate positioning with zero error was able to be achieved in the calculation results of the CFD model. Finally, the influence factors of the detection effect of this method were analyzed by inputting the determined disturbance signal. Both the disturbance signal characteristics and the leakage hole characteristics affected the reflected signal, and the former played a more prominent role. Surprisingly, the results showed that pipeline flow and pressure had very limited influence on this method.
The reliability of the compressor system determines the gas supply safety. An important method to improve the reliability is to set up standby compressors in stations, conducted by the standby ...compressor or power. A lack of quantitative assessments of standby compressors often results in more spare compressors or power than actually needed, which wastes money. In this study, a reliability-based method is proposed to determine the numbers and positions of the standby compressors, which can reduce investments, and ensure reliability. Firstly, Monte Carlo method was used to calculate the compressor outage probability of the whole pipeline, respectively, through which the initial number of standby compressors was obtained. Further, the standby schemes were designed, in which the positions of the failed compressors were obtained by the Monte Carlo simulation. Moreover, the worst situation in which the compressors were shut down was used to test the standby scheme, calculating the flow reliability, pressure boundary, and total power. Finally, using the Xin–Yue–Zhe pipeline as a case study, the results indicate that the number of standby compressors in the improved schemes was reduced by seven and the pipeline reliability reached 96.86%.
Cross-reactive neutralizing antibodies (NAbs) are found in the sera of many HIV-1-infected individuals, but the virologic basis of their neutralization remains poorly understood. We used knowledge of ...HIV-1 envelope structure to develop antigenically resurfaced glycoproteins specific for the structurally conserved site of initial CD4 receptor binding. These probes were used to identify sera with NAbs to the CD4-binding site (CD4bs) and to isolate individual B cells from such an HIV-1-infected donor. By expressing immunoglobulin genes from individual cells, we identified three monoclonal antibodies, including a pair of somatic variants that neutralized over 90% of circulating HIV-1 isolates. Exceptionally broad HIV-1 neutralization can be achieved with individual antibodies targeted to the functionally conserved CD4bs of glycoprotein 120, an important insight for future HIV-1 vaccine design.
The problem of data association for target tracking in a cluttered environment is discussed. In order to improve the real-time processing and accuracy of target tracking, based on a probabilistic ...data association algorithm, a novel data association algorithm using distance weighting was proposed, which can enhance the association probability of measurement originated from target, and then using a Kalman filter to estimate the target state more accurately. Thus, the tracking performance of the proposed algorithm when tracking non-maneuvering targets in a densely cluttered environment has improved, and also does better when two targets are parallel to each other, or at a small-angle crossing in a densely cluttered environment. As for maneuvering target issues, usually with an interactive multi-model framework, combined with the improved probabilistic data association method, we propose an improved algorithm using a combined interactive multiple model probabilistic data association algorithm to track a maneuvering target in a densely cluttered environment. Through Monte Carlo simulation, the results show that the proposed algorithm can be more effective and reliable for different scenarios of target tracking in a densely cluttered environment.
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A series of 4-hydroxyl aurone derivatives were designed synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease. The results ...demonstrated that most of the derivatives exhibited good multifunctional properties. Among them, compound 14e displayed good inhibitory activities of self- and Cu2+-induced Aβ1–42 aggregation with 99.2% and 84.0% at 25μM, respectively, and high antioxidant activity with a value 1.90-fold of Trolox. In addition, 14e also showed remarkable inhibitory activities of both monoamine oxidase A and B with IC50 values of 0.271μM and 0.393μM, respectively. However the 6-methoxyl aurones 15a–c revealed excellent selectivity toward MAO-B. Furthermore, the representative compounds 14e and 15b displayed good metal-chelating abilities and blood–brain barrier (BBB) permeabilities in vitro.
Amorphous indium-gallium-zinc oxide-based synaptic transistors with hafnium oxide (HfOx) insulating layer were fabricated to mimic synaptic long-term depression (LTD) characteristics. The fabrication ...temperature was less than 120°. Interval time of presynaptic spikes-dependent synaptic depression was first demonstrated in these IGZO-based synaptic transistors, which is important for computation system coding by time. The depression effect in our synaptic transistor is erasable, using ultraviolet light (\lambda = 365 nm) to erase the electrons trapped in the defects of the HfOx layer. Our device is in great significance for future brain-like artificial neuromorphic computation system since LTD has been verified as a contributor to learning and memory function in brains.
Ship-radiated noise is one of the important signal types under the complex ocean background, which can well reflect physical properties of ships. As one of the valid measures to characterize the ...complexity of ship-radiated noise, permutation entropy (PE) has the advantages of high efficiency and simple calculation. However, PE has the problems of missing amplitude information and single scale. To address the two drawbacks, refined composite multi-scale reverse weighted PE (RCMRWPE), as a novel measurement technology of describing the signal complexity, is put forward based on refined composite multi-scale processing (RCMP) and reverse weighted PE (RWPE). RCMP is an improved method of coarse-graining, which not only solves the problem of single scale, but also improves the stability of traditional coarse-graining; RWPE has been proposed more recently, and has better inter-class separability and robustness performance to noise than PE, weighted PE (WPE), and reverse PE (RPE). Additionally, a feature extraction scheme of ship-radiated noise is proposed based on RCMRWPE, furthermore, RCMRWPE is combined with discriminant analysis classifier (DAC) to form a new classification method. After that, a large number of comparative experiments of feature extraction schemes and classification methods with two artificial random signals and six ship-radiated noise are carried out, which show that the proposed feature extraction scheme has better performance in distinguishing ability and stability than the other three similar feature extraction schemes based on multi-scale PE (MPE), multi-scale WPE (MWPE), and multi-scale RPE (MRPE), and the proposed classification method also has the highest recognition rate.
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