Thermochemical treatment is a promising technique for biomass disposal and valorization. Recently, machine learning (ML) has been extensively used to predict yields, compositions, and properties of ...biochar, bio-oil, syngas, and aqueous phases produced by the thermochemical treatment of biomass. ML demonstrates great potential to aid the development of thermochemical processes. The present review aims to 1) introduce the ML schemes and strategies as well as descriptors of the input and output features in thermochemical processes; 2) summarize and compare the up-to-date research in both ML-aided wet (hydrothermal carbonization/liquefaction/gasification) and dry (torrefaction/pyrolysis/gasification) thermochemical treatment of biomass (i.e., predicting the yields, compositions, and properties of oil/char/gas/aqueous phases as well as thermal conversion behavior or kinetics); and 3) identify the gaps and provide guidance for future studies concerning how to improve predictive performance, increase generalizability, aid mechanistic and application studies, and effectively share data and models in the community. The development of biomass thermochemical treatment processes is envisaged to be greatly accelerated by ML in the near future.
In this paper, a moving-average method of smoothing noise based on complex exponential decomposition is applied to eliminate noise of a non-stationary signal and a non-linear signal produced by ...Bouc–Wen model, which are added to white Gaussian noise to simulate the noise in measured signal. The method uses a sliding window cutting the entire non-stationary and/or non-linear signal into small segments and considers that the small segments are stable and linear. The segments are decomposed into a series of components via complex exponential decomposition, and the high-energy components are reserved to reconstruct de-noised signal. Then, due to the overlap of the reconstructed segments, the average value at the same time point of reconstruction signal is regarded as the de-noised data. A non-stationary signal and a non-linear signal are selected to investigate the performance of the proposed method, the results show that the proposed method has better de-noising efficiency compared with the wavelet shrinkage method and the Savitzky–Golay filter method based on EMD (EMD-SG) for dealing with the signals with SNR of 10 dB, 15 dB, and 20 dB, and de-noised signal using the proposed method has the highest signal-to-noise ratio (SNR) and the least root mean square error (RMSE).
Converter valves are the core equipment of offshore wind power structures. However, they are highly vulnerable to vibration under strong earthquakes, which will affect normal operation of the ...offshore wind farm. Converter station is an axisymmetric structure with obvious asymmetry in its internal configuration of the superstructure. This study aimed to analyze the dynamic response of a supported converter valve in an offshore converter station under seismic excitation. The coupling model of the supported valve tower group and the converter station were established, and the distribution law of the valve tower dynamic response and foundation settlement were investigated. The dynamic response effect of the modal truncation, valve tower stiffness, and basic size on different areas and foundations of the valve towers were studied. The findings were as follows: (i) the effect of local vibration of the valve tower should not be simplified by using equivalent mass and node condensation; (ii) the structure–equipment coupling analysis method should be used to review the structural design scheme of the offshore converter station in the intensity VII region; (iii) the vertical higher-order modes should be considered during the vibration response calculation and its participation ratio in mass should not be lower than 90%; (iv) the frequency range that minimizes the vibration response is the characteristic frequency range of horizontal vibration, while the best vibration suppression effect cannot be obtained in both the horizontal and vertical directions; and (v) the stiffness of the valve tower itself should be adjusted and different stiffness designs of the valve tower in different positions should be adopted to realize effective vibration response control.
This study aims at proposing a simulation method for an offshore converter station platform (OCS) under dynamic loading. A user-defined in-house FORTRAN code was developed based on the Vector Form ...Intrinsic Finite Element (VFIFE) method, and the numerical model was validated by test data. After model validation, the dynamic behavior of the OCS was carefully studied and the effect of different loading conditions, including seismic, hydrodynamic and wind load, on the dynamic behavior of OCS was investigated. The time history of the structural response was obtained, and the relationship between the structural peak response and the peak value of the seismic load was also shown. It indicated that water damping accelerates energy consumption, while the effect of hydrodynamic and wind load has little influence on the cases studied in this work. Generally, the peak response increases almost linearly with the increase in the peak acceleration of the ground, and the seismic propagating direction has a great impact. In addition, both a whipping effect and stretching-squeezing effect were observed, and the vertical acceleration response of the valve hall deck is much higher than other structures, which is caused by the relatively lower local rigidity of the large-span structure and the inertia force caused by the valve tower.
Biochar production and application have become increasingly popular in the past 15 years. Biochar, derived from diverse biomass types, offers a rich carbon source created through thermal combustion. ...Biochar production primarily depends on pyrolysis conditions and feedstock type. This review focuses on the multifaceted aspects of biochar, encompassing hydrothermal carbonization, gasification, and pyrolysis temperatures in biochar production and its role in bioeconomy and soil remediation. Biochar has yielded valuable insights, notably in decreasing nutrient leaching, curbing greenhouse gas (GHG) emissions, reducing the bioavailability of environmental pollutants, sequestering carbon (C) in soils, and enhancing agricultural productivity. Consequently, it has emerged as a valuable commodity for the bioeconomy, which involves harnessing bioresources through bioengineering to create economically valuable products. As a marketable output, biochar finds application in energy, diverse biochar-based product manufacturing, and the agricultural sector. Thus, biochar production not only enhances soil quality but also unlocks additional revenue streams. This review underscores the critical role of feedstock selection and pyrolysis conditions in optimizing biochar production. Furthermore, it highlights biochar as a sustainable and effective tool for improving various soil types and remediating soil contamination caused by organic impurities, including persistent organic compounds and antibiotics.
Anonymity of mobile devices and their data is an essential requirement to facilitate the deployment of future Mobile Ad hoc Networks. The currently proposed anonymous routing mechanisms for such ...networks inherently include a trade-off between a high level of anonymity, performance and scalability. In this paper (parts of this paper have been published in TrustCom 2010), we propose an anonymous routing protocol that provides improved anonymity and security while achieving similar or better performance, as compared to existing proposals. Our proposal achieves anonymity using an efficient solution for invisible implicit addressing based on keyed hash chain and security via a novel application of one-to-many Diffie–Hellman mechanism, used to exchange keys for symmetric encryption. The final contribution includes a mechanism to facilitate selection of a trusted route by verifying connections between intermediate nodes. We demonstrate the benefits of our proposal in comparison with previous approaches using analysis and simulation.
The recently developed mobile network prefix provisioning (MNPP) enables a direct communication, i.e., Route Optimization (RO), between vehicular mobile routers (VMRs). However, without being ...secured, MNPP is vulnerable to various threats such as spoofing, replay, and wormhole attacks as well as location tracking. In this paper, possible threats to MNPP are identified with suggestions of security requirements. Then, three different security approaches (five different security mechanisms) for securing MNPP are introduced and compared.
The key concept of spectrum response estimation with commercial software, such as the SESAM software tool, typically includes two main steps： finding a suitable loading spectrum and computing the ...response amplitude operators （RAOs） subjected to a frequency-specified wave component. In this paper, we propose a nontraditional spectrum response estimation method that uses a numerical representation of the retardation functions. Based on estimated added mass and damping matrices of the structure, we de- compose and replace the convolution terms with a series of poles and corresponding residues in the Laplace domain. Then, we esti- mate the power density corresponding to each frequency component using the improved periodogram method. The advantage of this approach is that the frequency-dependent motion equations in the time domain can be transformed into the Laplace domain without requiring Laplace-domain expressions for the added mass and damping. To validate the proposed method, we use a numerical semi-submerged pontoon from the SESAM. The numerical results show that the responses of the proposed method match well with those obtained from the traditional method. Furthermore, the estimated spectrum also matches well, which indicates its potential application to deep-water floating structures.
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