Semi-submersible Offshore Coupled Motion in Irregular Waves

In order to predict the hydrodynamic performance of semi-submersible offshore platform accurately, based on CFD theory, continuous equation and N-S equation as the control equation, RNG type k-ε model as turbulence model, using the finite difference method to discretize the control equation，using the Semi-Implicit Method for Pressure Linked Equation (SIMPLE) algorithm to solve the control equation，using the VOF method to capture the free surface. The numerical wave tank of irregular wave is established, and the wave force and motion response of the semi-submersible platform under irregular wave are studied. Based on the Jonswap spectrum density function, for a certain area of two irregular waves (South China sea, a-ten-year return period, a-hundred-year return period) sea condition, five wave direction Angle (0 °, 30 °, 45 °, 60 °, 90 °), a total of 10 kinds of conditions of the motion response of semi-submersible platform are simulated, through analysis and comparison of simulation results, the influence law of wave angle, wave period and wave height on platform motion is obtained. Compared with the experimental values, the results of heave and pitch are close to the experimental data under the sea condition of 2, 0 degree wave angles. The research results in this paper can provide reference for the design and motion response prediction of practical semi-submersible offshore platforms

Hydrodynamic performance optimization of marine propellers based on fluid-structure coupling

Fiber-reinforced composites offer the benefits of high strength, high stiffness, lightweight, superior damping performance, and great design capability when compared to metal. The rigidity characteristics of the composite laminate in different directions may be adjusted to meet the requirements of the application by using appropriate materials and arranging the lay-up sequence. As a result, the purpose of this work is to explore the influence of lay-up type on propeller performance in terms of both hydrodynamic and structural performance. A transient fluid-structure interaction (FSI) algorithm based on the finite element method (FEM) combined with the computational fluid dynamics (CFD) technique is developed and used for the analysis of composite propellers. The hydrodynamic performance of the propeller is compared to that of a metallic material. Propeller propulsion efficiency, structural deformation, equivalent stress, and damage performance of different lay-up options under three different operating situations are compared. In addition, it is presented a parametric optimization approach to get the most appropriate lay-up program for composite blades with the best hydrodynamic properties and structural performance

Analysis and Research on the Characteristics of COVID-19 Epidemic in Urban Village and Its Prevention and Control Strategies in Primary Care Institutions

BackgroundFor a period of time, the outbreak of the COVID-19 outbreak in many urban villages in our country had caused concern. The dense and complex population structure of urban villages, with their inter-regional mobility, posed a challenge to the prevention and control of the epidemic.ObjectiveUrban village areasare more prone to regional outbreaks of infectious diseases because of their spatial environment, demographic characteristics, cross-regional mobility and the characteristics of residents' medical treatment behavior. The purpose of this study was tounderstand the characteristics of the COVID-19 epidemic situation in urban villages and the current situation and difficulties of primary care institutions in carrying out COVID-19 epidemic prevention and control measures, in order to provide references for primary care institutions to deal with normalized prevention and control, social dynamic clearing work and future infectious disease prevention and control.MethodsBy using public opinion analysis, literature retrieval, online interviews with epidemic prevention and control personnel and experts in urban village, the epidemic situation, prevention and control status of urban village were summarized, and the existing weak links and important loopholes were analyzed.ResultsBased on the relevant information, a total of six points of concern were extracted: (1) The number of mapping and screening objects was large, which was the focus and difficulty of epidemic prevention and control work in urban villages. (2) There was not strict closed-loop management lead to virus carriers who were not timely controlled, which caused a risk of spreading the epidemic. (3) The prevention and control of nosocomial infection in primary care institutions was not in place. (4) There were loopholes in the inspection of close contacts in the principle of territorial management; close contacts who did not live and work in the same administrative area but only screened in their living places, which may lead to the spread of the epidemic in workplaces where secondary close contacts may be at risk of infection were not screened in a timely manner. (5) Overload had become the norm, highlighting the large gap in primary health care manpower. (6) During the normalization of epidemic prevention and control, residents were paralyzed and careless, and the phenomenon of not wearing masks in public places and crowd gathering was common. Health education still needs to be strengthened and emphasized that residents were the first responsible for their own health.ConclusionPrimary care providers played an important role in the prevention and control of COVID-19 in urban village by undertaking community management, outpatient treatment, public health services, health education, vaccination, quarantine hotel stationing, joint prevention and control, etc. It was recommended that additional fever sentinel clinics be set up for early detection and isolation to avoid further spread of the epidemic, rental houses be requisitioned to meet the demand for isolated medical observation, primary care institutions be strengthened for hospitalization and prevention, green relief channels be opened to protect special groups from medical treatment, volunteers be organized to reinforce primary care institutions, and health education emphasized that residents were the first to be responsible for maintaining their own health and raised personal awareness of the risk of COVID-19 prevention and control

Research on the Filters for Dual-Inverter Fed Open-End Winding Transformer Topology in Photovoltaic Grid-Tied Applications

Owing to the necessity of the transformer for the multi-parallel inverters connected to the medium-voltage (MV) grid, the conventional multi-parallel inverter topology can be reconfigured to the dual-inverter fed open-end winding transformer (DI-OEWT) topology to obtain lower output voltage harmonics, which can reduce the requirement of the filter inductance. However, due to the special structure of the DI-OEWT topology, the arrangement scheme of the filter can be more than one kind, and different schemes may affect the filter performance. In this paper, research on the existing two kinds of filters, as well as a proposed one, for the DI-OEWT topology used in photovoltaic grid-tied applications is presented. The equivalent circuits of these filters are derived, and based on this, the harmonic suppression capability of these filters is analyzed and compared. Furthermore, a brief parameter design method of these filters is also introduced, and based on the design examples, the inductance and capacitance requirements of these filters are compared. In addition, these filters are also evaluated in terms of the applicability for fault tolerance. At last, the analysis is verified through an experiment on a 30 kW dual-three-level inverter prototype

DFT, EPR and SPR insight to the relation between photocatalytic activity and nonlinearity and anisotropy ferromagnetism of Au/Co3O4/Bi2MoO6 composites

The combination of Surface Plasmon Resonance (SPR) effect with hetero-p-n structure has shown promising benefits to photocatalytic activity of catalysts. In this study, Au nanoparticles doped p-n hetero-structured Co3O4/Bi2MoO6 composites were synthesized and subjected to photocatalytic and photocurrent tests using visible light irradiation. The synthesized Au/Co3O4/Bi2MoO6 efficiently removed 97.2% of Methyl orange within 60 min, showing very good photocatalytic stability through leaching test. Colorless pollutant phenol degradation test verified the excellent photocatalytic activity of Au/Co3O4/Bi2MoO6. Possible influential factors such as electron transition, charge transfer, energy band gap, DOS, polarizability, SPR effect, oxygen vacancies and anisotropy permittivity were investigated through DFT, XPS, EPR, Z-scan, UV–visible spectra, ellipsometer spectroscopy and Mott-Schottky analysis. A reasonable degradation mechanism and possible pathway for Methyl orange were proposed based on the experimental results and DFT calculations. The doped Co3O4 provided active 3d electrons transition and charge transfer which increased carriers’ con centration and reduced the energy band gap, while the Au SPR enhanced internal polarization and strengthened the built-in electric field, yielding strong driving force for photo-generated electrons-holes pairs separation and consumption. In addition, magnetic Co3O4 endowed sample with room-temperature ferromagnetism which was obviously strengthened by Au NPs. The magnetism of sample was beneficial for separation and recovery in photocatalytic practical applications.

A Transferable Thruster Fault Diagnosis Approach for Autonomous Underwater Vehicle under Different Working Conditions with Insufficient Labeled Training Data

Existing thruster fault diagnosis methods for AUV (autonomous underwater vehicle) usually need sufficient labeled training data. However, it is unrealistic to get sufficient labeled training data for each working condition in practice. Based on this challenge, a transferable thruster fault diagnosis approach is proposed. In the approach, an IPSE (instantaneous power spectrum entropy) and a STNED (signal-to-noise energy difference) are added to SPWVD (smoothed pseudo Wigner-Ville distribution) to identify time and frequency boundaries of the local region in the time-frequency power spectrum caused by thruster fault, forming a TFE (time-frequency energy) method for feature extraction. In addition, the RCQFFV (relative change quantity of the fault feature value), an MSN (multiple scale normalization) and a LSP (least square prediction) are added to SVDD (support vector data description) to align distributions of fault samples, contributing a TSVDD (transferable SVDD) for classification of fault samples. The experimental results of a prototype AUV indicate that the fault feature is monotonic to the percentage of thrust loss for the proposed TFE but not for the SPWVD. The TSVDD has a higher overall classification accuracy in comparison to conventional SVDD under working conditions with no labeled training data

Template‐based and free modeling of I‐TASSER and QUARK pipelines using predicted contact maps in CASP12

We develop two complementary pipelines, “Zhang‐Server” and “QUARK”, based on I‐TASSER and QUARK pipelines for template‐based modeling (TBM) and free modeling (FM), and test them in the CASP12 experiment. The combination of I‐TASSER and QUARK successfully folds three medium‐size FM targets that have more than 150 residues, even though the interplay between the two pipelines still awaits further optimization. Newly developed sequence‐based contact prediction by NeBcon plays a critical role to enhance the quality of models, particularly for FM targets, by the new pipelines. The inclusion of NeBcon predicted contacts as restraints in the QUARK simulations results in an average TM‐score of 0.41 for the best in top five predicted models, which is 37% higher than that by the QUARK simulations without contacts. In particular, there are seven targets that are converted from non‐foldable to foldable (TM‐score >0.5) due to the use of contact restraints in the simulations. Another additional feature in the current pipelines is the local structure quality prediction by ResQ, which provides a robust residue‐level modeling error estimation. Despite the success, significant challenges still remain in ab initio modeling of multi‐domain proteins and folding of β‐proteins with complicated topologies bound by long‐range strand‐strand interactions. Improvements on domain boundary and long‐range contact prediction, as well as optimal use of the predicted contacts and multiple threading alignments, are critical to address these issues seen in the CASP12 experiment.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142472/1/prot25414_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142472/2/prot25414-sup-0001-suppinfo1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142472/3/prot25414.pd

Al3O4 tailored La0.8Sr0.2FeO3 crystallization in heavy metal oxide glass: synthesis, structure, and enhanced linear & nonlinear properties

Glass containing magnetic nanocrystals are attractive to provide high optical linear and nonlinearity properties. In this study, we reported the synthesis of perovskite La0.8Sr0.2FeO3 nanocrystals in heavy metal oxide glass under the AlO3 tailoring. The influence of AlO3 amount to the formation of La0.8Sr0.2FeO3 nanocrystals and the influence of nanocrystals to glass structure, optical linear& nonlinear properties were thoroughly investigated. The 10 nm-nanocrystals of orthogonal La0.8Sr0.2FeO3 were synthesized by melting quenching followed with subsequent crystallization process at 400 degrees for 30 min under the tuning of AlO3. The formed La0.8Sr0.2FeO3 were well distributed in matrix without aggregation. Structure and chemical valence study revealed the aluminum abnormality effect and the Sr2+ induced multi-valence states of Fe ions and oxygen vacancies in La0.8Sr0.2FeO3 lattice. Such modification clearly influenced the optical ab-sorption, refractive index, polarizability, energy band gap shrinkage and nonlinearity. Physical parameters such as oxygen packing density, free volume etc. were calculated to confirm the influence of AlO3 tailored La0.8Sr0.2FeO3 crystallization to glass. The glass with 10%AlO3 amount exhibited a large thermal stability (132 degrees), low thermal expansion coefficient (10.2 x10(-6)/K) and high BO4/AlO4 units, providing suitable environment for La0.8Sr0.2FeO3 crystallization. About 20 nm nanocrystals were formed and well distributed in glass which contributed to large nonlinearity absorption coefficient (5.19 x10(-10) m/W) and FOM (13.6 x10(3) esu cm) which much superior than from relative literatures. The obtained glass with extremely good optical linear and nonlinearity performances can be promising candidate for photonics device applications. (C) 2022 Elsevier B.V. All rights reserved