Search

Based on the recently proposed power-law spectrum for oceanic turbulence [Opt. Express 26 , 10188 (2018)] and the Rytov approximation, the new and exact theoretical forms for the wave structure function (WSF) of plane and spherical waves propagating in turbulent ocean are derived. To make the results easy to use, the simple formulas for the WSF and the associated spatial coherence radius in certain asymptotic regimes are also developed. Through numerical analysis, it is found that the existing results based on the Nikishov's spectrum predict a higher values for the WSF and thus a lower values for the spatial coherence radius than our results. [ABSTRACT FROM AUTHOR]

In this manuscript, the samples were collected from Weiyuan Investment Group. The basic properties of the oil-based drill cuttings and their pyrolysates were analyzed. The results show that the oil content of the oil-based drilling cuttings is 7.87%, and the average calorific value of pyrolysis gas is about 20,327 kJ m−3. In the component of gas, hydrogen accounts for 30.64% and CO2 accounts for 43.34%. The main components of pyrolytic oil are diesel fraction, of which the H/C ratio is 1.90 and the linear alkane is the main component, accounting for 65.65%. And the carbon number of the pyrolytic oil is mainly distributed in C12~C25. The pyrolytic products possess high value of recycling. The pyrolysis kinetics of oil-based drilling cuttings was studied by developing different kinetic models. Firstly, the mass loss of oil-based drilling cuttings can be divided into two stages. The first stage consists of the evaporation of water and the volatilization of small molecular organic compounds. The second stage is the main pyrolysis process which contents the breaking of carbon–carbon bond, and the thermogravimetric curve shifts to the high temperature region with the increasing of heating rate. The calculated results of different kinetic models show that the fitting degree of the two models is high. According to the calculated results using Friedman model, the pyrolysis stage of oil-based drilling cuttings increases from about 73 kJ mol−1 to about 109 kJ mol−1. According to the calculated results using DAEM model, the activation energy increased from about 63 kJ mol−1 to about 80 kJ mol−1. The results can help provide experimental data for industrial processing of oil-based drilling cuttings in Weiyuan Investment Group. [ABSTRACT FROM AUTHOR]

This paper proposes a new belief rule-based (BRB) expert system for fault diagnosis of marine diesel engines. The expert system is the first of its kind that consists of multiple concurrently activated BRB subsystems, in which each subsystem has its distinctive outputs and uses the evidential reasoning approach for inference. This novel modeling approach can be applied to identify fault modes that may co-exist. In essence, the group of BRB subsystems is used to model the nonlinear relationships between the fault features and the fault modes in marine diesel engines. The initial BRB expert system can be established by using expert experience and then optimized by using the data samples accumulated during the operation of marine diesel engines. Due to limitations in knowledge and data collected, ignorance is also considered in some BRB subsystems. The proposed BRB expert system is applied to abnormal wear detection for a kind of marine diesel engine. The performance of the BRB expert system is investigated in comparison with that of artificial neural network (ANN) models, support vector machine (SVM) models, and binary logistic regression model with fivefold cross-validation. The results show that the BRB expert system can be used for fault diagnosis of marine diesel engines in a probabilistic manner, which outperforms the ANN models, SVM models, and the binary logistic regression model in terms of accuracy and stability, and can effectively identify concurrent faults. [ABSTRACT FROM AUTHOR]

Multiple-input single-output (MISO) have extraordinary propagation properties, making it possible to further improve the performance of underwater wireless optical communication (UWOC). In this paper, a tilted MISO-UWOC system consists of a beam array and an aperture averaged detector, academically called multiple-input aperture-average (MIAA) systems, are proposed. Different from the original approach where beams are parallel to each other, the tilted approach has a series of multiple beam transmitters individually aimed at the receiver. The MIAA systems are extensively compared to single-input single-output (SISO) systems on scintillation index and SNR for various oceanic turbulence conditions and system configurations by wave optics simulation (WOS). Our results reveal that tilted MIAA systems show tremendous advantages over the parallel MIAA systems including the reduced scintillation and the improved signal to noise ratio (SNR) under the same configuration. The obtained results can be useful for the UWOC system design. [ABSTRACT FROM AUTHOR]

The water-lubricated thrust bearings of the marine Rim-Driven Thruster (RDT) are usually composed of polymer composites, which are prone to serious wear under harsh working conditions. Ultrasonic is an excellent non-destructive monitoring technology, but polymer materials are characterized by viscoelasticity, heterogeneity, and large acoustic attenuation, making it challenging to extract ultrasonic echo signals. Therefore, this paper proposes a wear monitoring method based on an improved ultrasonic reflection coefficient amplitude spectrum, introducing an ultrasonic transfer function to mathematically resolve the attenuation coefficients in the propagation model, and using a differential evolutionary algorithm to invert the thickness, sound velocity, density, and attenuation coefficients of polymer bearings simultaneously. The effects of different influencing factors on the ultrasonic signal and identification results are explored, including probe contact pressure, surface roughness and surface inclination; In order to remove the influence of water film overlap on the identification of polymer bearing thickness, a water film separation method based on time-frequency domain ultrasonic reconfiguration is proposed to construct the ultrasonic theoretical time domain waveform of the bearing. An ultrasonic wear measurement system is built to record the ultrasonic echoes of PEEK test blocks with different pressures to the probe, surface roughness, and tilt angles. The experiment is carried out on the water film calibration test rig, using a high-precision spiral micrometer to simulate the mixing of water films of different thicknesses with polymer test block and collecting ultrasonic signals. The results show that the method has a thickness identification error of approximately 0.5% for PEEK specimens with different probe contact pressure, roughness, and tilt angle, and the reconfiguration thickness identification error is less than 1% for the full range of water film overlap. • Propose a wear monitoring method based on an improved ultrasonic reflection coefficient amplitude spectrum, introducing an ultrasonic transfer function to mathematically resolve the attenuation coefficients in the propagation model. • A water film separation method based on time-frequency domain ultrasonic reconfiguration is proposed to construct the ultrasonic theoretical time domain waveform of the bearing. • Use a differential evolutionary algorithm to invert the thickness, sound velocity, density, and attenuation coefficients of polymer bearings simultaneously. • The method has a thickness identification error of approximately 0.5% for PEEK specimens with different probe contact pressure, roughness, and tilt angle, and the reconfiguration thickness identification error is less than 1% for the full range of water film overlap. [ABSTRACT FROM AUTHOR]

Drug solubility and lymphatic transport enhancements are two main pathways to improve drug oral bioavailability for microemulsions. However, it is not easy to have both achieved simultaneously because excipients used for improving lymphatic transport were usually insufficient in forming microemulsions and solubilizing drugs. Our research is to explore whether ethyl oleate, an oil effective in developing microemulsions with desired solubilizing capability, could increase bioavailability to a higher extent by enhancing lymphatic transport. As a long-chain oil, ethyl oleate won larger microemulsion area than short-chain tributyrin and medium-chain GTCC. In contrast, long-chain soybean oil failed to prepare microemulsions. The solubility of piroxicam in ethyl oleate microemulsions (ME-C) increased by about 30 times than in water. ME-C also won significantly higher AUC 0−t compared with tributyrin microemulsions (ME-A) and GTCC microemulsions (ME-B). Oral bioavailability in ME-C decreased by 38% after lymphatic transport was blocked by cycloheximide, severer than those in ME-A and ME-B (8% and 34%). These results suggest that improving lymphatic transport and solubility simultaneously might be a novel strategy to increase drug oral bioavailability to a higher extent than increasing solubility only. Ethyl oleate is a preferred oil candidate due to its integrated advantages of high solubilizing capability, large microemulsion area and effective lymphatic transport. [ABSTRACT FROM AUTHOR]

This paper presents a procedure for the optimal design of industrial alarm systems based on evidence theory to deal with epistemic and aleatory uncertainties of the monitored process variable. First, the upper and lower fuzzy thresholds are designed, and then the sampled value of the process variable is transformed into a piece of alarm evidence to measure the degrees of uncertainty about whether an alarm should be triggered or not by the sampled value. Second, a linear updating rule of evidence is recursively applied to combine the updated alarm evidence at t −1 step with the incoming alarm evidence at t step to generate the updated alarm evidence at t step. In the process of evidence updating, the weights of evidence for linear combination can be obtained by dynamically minimizing the distance between the updated alarm evidence and the true mode (i.e., “alarm” or “no-alarm”). An alarm decision can then be made according to a pignistic probability transformed from the updated alarm evidence at each time step. Finally, numerical experiments and an industrial case are given to show that the proposed procedure has a better performance than the classical design methods. [ABSTRACT FROM AUTHOR]

In the evidential reasoning (ER) approach, in addition to the weight of a criterion, reliability is another important concept in connection with the criterion although it attracts little attention. Additionally, a decision maker's risk attitude is of particular importance in decision-making. To simultaneously consider these two important factors, this paper proposes a new ER approach. In the approach, with the consideration of a decision maker's risk attitude, the combinational reliability of each criterion for each alternative is constructed from the original reliability of the criterion. By following the regression idea to learn the original reliability of each criterion, a unified optimization model is constructed, in which the maximum difference between combinational reliabilities and their estimations is minimized. Within the post-optimal solution space of criterion reliabilities found by solving the unified model, another optimization model is constructed, from which the minimum and maximum expected utilities of each alternative are determined. Solutions to multi-criteria decision-making problems are then generated from the expected utilities. The proposed approach is used to analyze a material supplier selection problem for a company located in Tongling, Anhui, China. The analysis of the problem demonstrates the applicability of the proposed approach. [ABSTRACT FROM AUTHOR]